INSTALLING DOMESTIC ELECTRICAL DEVICES

INSTALLING DOMESTIC ELECTRICAL DEVICES

1

1

Super Power Stations

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Class Number

86, St. Peter's Grove,Canterbury.

17th Dec., 1934.L 131682.Dear Sir,

You may remember me as a pupilof your College, taking a correspondencecourse for the recent Civil ServiceExamination. The result of this examina-tion has now been published and I learnthat I was fortunate enough to secure thetop place out of over 1,400 other candidates .I consider that this result reflects greatcredit upon your course and your tutors,for their interest and their willingness tohelp me with my studies.

May I wish you the compliments ofthe season and every success in the future.

Yours very gratefully,C. P. Cayley.

3LETTERSRead them then youwill realise what is

happening and why.

A VOCATIONAL TRAINING

FROM THIS COLLEGE IS A

CAREER -A SUCCESSFUL

PROGRESSIVE CAREER

110, Victoria Road, Dundee,Angus.

16th January, 1935.

MR. J. H. BENNETT,Bennett College Ltd.,

Sheffield.

Class Number L159929.

Dear Sir,A short time ago I enrolled as a

student of the Clerk of WorksArchitecture, etc., course ; although stillin my twenties, I have, through theexcellent tuition provided in the abovecourse, been successful in my applicationfor the position as Clerk of Works withthe Dundee Town Council.

Yours faithfully,George Moffat.

OPEN LETTER TO PARENTSDear Sir or Madam,-When your children first arrived they brought with them a wonderful lot of sunshine. Later you becameproud of the intelligence they displayed, but still later you became anxious as to what would become of them in the future. Perhapsyou were anxious when you visualised them as grown men and women. Even with plenty of money it is not always easy to selectthe right career, and a parent is sometimes inclined to ask advice of some relative and in ninety-nine cases out of a hundredthat relative knows nothing at all about the possibilities of employment. Why not let me relieve you of some of your anxieties?In fact, why not let me be their Father ? We do not profess to act as an employment agency, but the nature of our business com-pels us to keep an eye upon the class of men and women that are wanted and who wants them. There are some people whomanufacture an article and put it on the market to sell. We do not do that, we work in exactly the opposite direction. We find outwhat employers want and we train our students to fill those jobs. We have to be experts in thematter of employment, progress and prosperity. If you have any anxieties at all as to what yoursons and daughters should be, write to me, or better still, let them write to me personally --Fatherly Advice Department-and tell one their likes and dislikes, and I will give sound, practicaladvice as to the possibilities of a vocation and how to succeed in it. Yours sincerely,

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There are hundreds of openings in connection withHumorous Papers, Advertisement Drawing, Posters,Calendars, Catalogues, Textile Designs, Book

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May, 1935 NEWNES PRACTICAL MECHANICS 345

ractica1MAY

VOL. II. No. 20

MechanicsSUBSCRIPTION RATES :

Inland and Abroad, 7s. 6d. per annumCanada - - 7s. per annum

Editorial and Advertisement Offices : " PracticalMechanics," George Newnes Ltd., Southampton

Street, Strand, W.C.2.Registered at the G.P.O. for transmission by

Canadian Magazine Post.

Notes, News and ViewsA Vertical Flight

THE autogiro, which is now in extensiveuse, has at last achieved a direct lift off

the ground without any forward run. Thisamazing performance will thus enable themachine to rise in a very restricted area.The autogiro has already shown its abilityto ascend with a very short run and toalight in confined spaces.Into the Stratosphere

WE learn that a rocket is being preparedby Russian scientists which, they

declare, will be capable of reaching a heightof 28 miles. A small model of the rocket,weighing only 33 lb., and propelled by amixture of benzene and liquid oxygen, willbe tried out at a Moscow aerodrome. Thisis expected to rise to a height of 2i miles,where it will automatically release its baro-graph, which will descend safely by para-chute.

A New Streamlined Express

THEG.W.R. express, " King Henry VII,"

has recently been streamlined at Swin-don. It has been fitted with a " bulletnose " front to reduce wind resistance, andcertain modifications have been made tothe boiler, cab and tender by use of lightsteel plates.A DiscoveryANEW land, which has been named

Ingrid Christensen's Land, has been dis-covered in the Antarctic by a Norwegianoil tanker, " The Throshavn." Possessionhas been taken in the name of Norway.World's Largest Airship

THE new German dirigible, " LZ 129,"the biggest in the world, is expected to

be launched this month. With this airshipthe designer, Dr. Eckener, claims that theperformance of the " Graf Zeppelin " will begreatly surpassed. It will be able to crossthe Atlantic in forty-eight hours westwardand in fifty-five hours eastward. The" LZ 129," which is nearly twice the sizeof the " Graf Zeppelin," will be capable of aspeed of 83 m.p.h. and will carry fifty pas-sengers and a crew of fifty-four. She is813 ft. in length, and will contain 6,710,000cub. ft. of gas as compared with " GrafZeppelin," 3,709,000 cub. ft., the late. U.S." Macon," 6,500,000, and the two defunctBritish airships, 5,000,000 cub. ft. The" LZ 129 " is to be fitted in part withengines of the Diesel type.

The World " on the Phone "THE recent successful inauguration of the

Anglo-Japanese radio -telephone servicenow makes it possible for a telephone sub-scriber in Britain to piok up his receiverand call Tokyo. The minimum coat for thiswill be £6 for three minutes. The new Japanservice is limited to the period between 8a.m. and midday, English time (5 to 9 p.m.in Japan).

THE MONTH'S SCIENCESIFTINGS

Lighter aeroplanes capable of a speed of275 m.p.h. will be under constructionbefore the end of this year in preparationfor competitive tests.

A streamlined and petrol -driven pneu-matic-tyred train reached a speed of 65m.p.h. during a recent demonstration run.

To minimise as far as practicable inter-ference with wireless programmes, all newtrolley buses will be fitted with stopper coilsor other apparatus.

During 1934 the R.A.F. flew about400,000 hours, a computed distance of47,000,000 miles, at an average speed of116 m.p.h.

The world's first high -definition televisionservice was recently opened in Berlin.

The discovery of an uncharted sub-marine mountain ridge in the AtlanticOcean, 180 miles south-west of Portugal,has been made by the cable ship Ampere "whilst repairing cable from Brest toCasablanca.

An Experimental " Air Train "I T is stated that experiments are beingcarried out in Moscow for an aeroplane

to tow nine gliders from Moscow to Irkutsk,a distance of 3,000 miles. To avoid colli-sions in mid-air the gliders will be towed atdifferent levels. Regular lines may beestablished if the above experiment provessuccessful.

" Thermometer " TuningAUNIQUE development in wireless

receivers is " thermometer " tuning,introduced by Messrs. A. C. Cossor Ltd.Station names and wavelengths are instantlyvisible on an illuminated scale, and as thetuning knob is turned a dark column risesand falls, giving immediate and accuratetuning of stations.

Long-playing Gramophone NeedlesANEW gramophone needle has recently

been produced by H.M.V. researchengineers. These high-fidelity needles willplay thirty to sixty record sides withoutcausing serious high -note loss when used onan ordinary acoustic or radio -gramophone.This is a record track length of about 5 miles.

30,000 Feet above the AtlanticAN Irishman, Mr. C. L. Fowey, has in-

vented several devices designed toincrease safety, weight -lifting capacity andspeed of an aeroplane. He hopes to demon-.strate their efficiency by a return Atlanticflight in an aeroplane that is being secretlyconstructed in New York. Mr. Foweyintends to fly at a height of 30,000 ft. duringthe flight, and the plane will be fitted witha two-way telephone apparatus with whichhe intends to keep in touch with Americaand Europe. To generate the necessaryelectrical power to make this possible theinventor proposes to occasionally make along dive at a high speed towards the ocean.Mr. Fowey will carry an oxygen supply andbe enclosed in an almost hermetically -sealed cabin.

Television To -day

ON April 10th was published the firstnumber of a new serial work entitled

" Television To -day " ( Is.). It is to be com-pleted in about sixteen weekly parts.

One of the most interesting features inNo. 1 is a survey covering all the chiefsystems used in this country, in Germany,and in the U.S.A.

In the list of contributors we notice manywell-known names, notably Dr. V. K.Zworykin, the inventor of the Iconoscope ;Philo Farnsworth, the inventor of theElectron Image Dissector ; and Capt.A. G. D. West, the Technical Director of theBaird Co. A splendid shillingsworth for theman who wishes to bring his knowledgeright up to date on this new phase of radio.

A New Safety RazorANEW type of safety razor, the blade

of which consists of a narrow ribbon ofsteel 57 in. in length, is now being manu-factured in Sheffield. The blade, which isfitted on two spools, works on the sameprinciple as a typewriter ribbon, and whenthe length of blade in use becomes blunt afresh length is brought into use by turningthe blade on the spool.


346 NEWNES PRACTICAL MECHANICS May, 1935

TO visit any vast electric powerstation is to feel suddenlydwarfed by the majesty of

things mechanical, as though anentry had been vouchsafed to someinfinitely more progressive planetor remotely future age. Almost itmight seem that whatever is dealtwith fantastically to -day is by some-one made practicable to -morrow.

The power station at Barking,built on the left bank of theRiver Thames, is the largest inthis country. The original building,containing 100,000 kw. of plant, wasopened by H.M. the King in 1925. By 1931the plant installed totalled 240,000 kw.,and in 1932 the recent extensions, whichcomprise two units of 75,000 kw. each,were embarked upon, bringing the presentinstalled capacity of the whole station upto 390,000 kw. If this huge plant wereworking continuously throughout the yearand at full capacity, it would generate3,400 million units-more than a quarterof the units turned out in the whole ofGreat Britain.Efficiency the Keyword

The two newer turbines are housedimposingly. The network of pipes on roofand walls is variously coloured, each colourdenoting the work the pipe is doing. Thegrey, aluminium and black of the machinesand boilers make an impressive background.Efficiency has been the keyword from firstto last. The two new turbo -alternators arethe largest in service in Great Britain, andare connected to the two largest trans-formers in the world, each of the lattercontaining forty-three miles of copper'winding and weighing 120 tons. No bridgewas strong enough to bear these hugetransformers on their journey to Barking,and they had to be transported across theriver on special ferries. Yet even they intheir present setting are dwarfed by theimmensity of their surroundings.

' The energy from the Barking turbinesleaves the station both above ground and I

Nowhere is the Harnessing of GiantMachinery to the Service of Mankind moreImposingly Demonstrated than in theWorld's Great Electrical Power Stations.The Photographs and the Text of thisArticle deal interestingly with someof the Finest Examples of Electro-Generating Machinery in Existence

below ground. Below the bed of the RiverThames a tunnel 7 ft. in diameter carriesthe output cables to south-east London, toSurrey, and to Kent. Westward from thestation, underground cables feed the eastLondon areas. The overhead lines branchnorthward and eastward into Essex andbeyond, whilst the whole of the trans-mission system is dominated by two

towers-the highest of their kind inthe world-one on each bank ofthe river.

The Coal ConveyorsThe coaling jetty is about

1,000 ft. long, from which two shipsof approximately 4,000 tons apiececan be unloaded simultaneouslyby six cranes at the rate of noless than 1,200 tons per hour.Belt conveyors, linking jetty andstation, can carry 1,400 tons

per hour. About half a million tons ofcoal per annum are used. The newboiler house contains eight boiler units,burning stoker -fired coal, and having anormal evaporative capacity all told of1,350,000 lb. of steam per hour, as con-trasted with a normal evaporative capacityof 2,166,000 lb. of steam per hour obtain-able from the twenty-six older boiler unitsinstalled.

New TurbinesThe illustration on the cover gives a

clear idea of the impressive proportions ofthe new 75,000 -kw. turbo -alternators.They were built partly in the Rugbyworks of the B.T.H. Company and

The two 75,000 -kilowatt turbo -generators at Barking Power Station.



0140 141t 0,ol111a..to4%,

II. 4444.. **

partly in the Trafford Park works of theMetropolitan -Vickers Electrical Company.The normal pressure of the superheatedsteam at entry is 600 lb. per squareinch with a maximum of 700 lb. persquare inch, the temperature being800° F. or more. The turbines havethree cylinders each-high-pressure, inter-mediate -pressure, and low-pressurerespectively-steam passing from the highto the low as it expands and delivers upits store of energy. All connectionsbetween the steam chests and the high-pressure cylinders are below floor level.Efficient glands prevent discharge of steaminto the turbine room. Flexible or semi -flexible couplings connect the high, inter-mediate, and low-pressure rotors and thealternator rotor, the axes of all four being,of course, in line. The freedom of the systemsfrom vibration and noise is remarkable.

Safety DevicesIngenious emergency

valves are fitted. Inthe event of overspeed,a governor wouldtrip a valvecontrolling thesupply of oil tothe operatingcylinders of theemergency

On the left is shownthe control room withits multitude of dials,and below an exampleof heavy - voltage

switchgear.

valves, whichwould in turnclose under theaction of springloading andsteam pressure.As an addedprecaution thegovernor valves controlling the admissionof steam to the high-pressure cylinderwould also close. Failure in the lubricationsystem would similarly be the means ofcalling a halt before damage was done.Means are provided for limiting by handthe maximum valve opening on each steamchest in the feed system, so that the loadon the unit can be predetermined and cannotbe exceeded.

Weights of the component parts of thealternators are : stator, 150 tons ; rotor,72 tons and exciters, 10 tons. A radial -impeller -type blower, of 12 tons, with acapacity of 100,000 cub. ft. of air perminute is coupled to the end of eachalternator shaft for ventilation purposes.

Boilers and FurnacesThe steam -raising equipment consists of

eight Babcock and Wilcox boilers installedin two towering lines. Between the top ofthe grate and the underside of t}.^ firstrow of boiler tubes themean height of the

Lfurnaces alone, with water-cooled walls onall sides, is 23 ft. Each water wall forms aseparate unit connected to the boiler drumby its own downcomers ajid risers. Thetravelling grates of the stokers are 30 ft.wide and 22 ft. 6 in. long, giving an effectivearea of 675 sq. ft. An independent airsupply has been provided for each grate.

Secondary air is admitted fairly high in thecombustion chamber, so that it intermingleswith the gases in the hot combustion zoneand creates complete combustion. Eachboiler has two forced and two induceddraught fans. Automatic control isadopted, the object being to maintain aconstant suction in the furnace even underforced -draught conditions. A boiler instru-ment panel associated with each boilerprovides every conceivable indication ofthe conditions under which the boiler isworking, and even, by means of a photo -

Barking Power Station rem the river, showing the coal cranes and conveyors.



electric cell device, indicates the densityof the smoke ascending the chimneys.

Before the water is allowed to enterthe boiler system it is first softened in aspecial water -softening plant, and alsochlorinated in the chlorinating plantillustrated. Softening the water preventscalcium deposits occurring on the innersurfaces of pipes, etc., and chlorinating thewater prevents fungoid growths whichmight otherwise be set up.

SwitchgearEach of the switch -house buildings com-

prises two wings, part of one of which isshown in one of our illustrations. Toprevent incorrect operation there is a systemof mechanical and electrical interlocking.The control room shown in another illustra-tion contains new Reyrolle equipment.

Current is distributed from Barking overa very large area, including the centralboroughs of Finsbury and parts of Holborn,Bermondsey, and Southwark, and branchinginto Essex, Kent, and Surrey. Additionally,

A battery of feed heaters and pumps.

electricity is supplied for traction purposesto the London, Midland and ScottishRailway, and the London Passenger Trans-port Board (Morden Tube).

Extensive Use of GlassTurning for a moment exclusively to the

new building, glass has been used exten-sively, resulting in well -lit plant and officeaccommodation. Above the structure, com-posed of red brick and white stone, glassoccupies three parts of the total height onthree sides of the building. The four brick -built chimneys are 250 ft. high, and taperfrom 30 ft. at the base to 23 ft. at the top.An important difference between the oldstation and the new is that the generatingunits in the new turbine -room do not usepulverised fuel and steam re -heating equip-ment, and are arranged longitudinally asillustrated on the first page of this article in-stead of crosswise. Again, of course, the newmachines are on an altogether larger scale.

In conjunction with the extensions men-tioned, steps have been taken with regardto possible further extension, and the lay-out of the new buildings has been plannedwith that end in view. The new unloading

The chlorinating plant by means of which one part of chlorine isintroduced into each four million parts of water to prevent

subsequent fungoid growths in the circulatory system.

jetty and river wall is capable of dealingwith a further addition to the station. Itwas considered thus necessary to be pre-pared for eventualities in view of thegreatly increased demand made for elec-tricity, more particularly for domestic pur-poses. The vast public living within thearea of supply are finding it increasinglyconvenient to cook by electricity and heatwater by electricity, apart from its universaluse for lighting purposes.

Weighing the FuelAll incoming coal can be weighed, hopper

weighing machines being provided for thepurpose on two of the cranes. From the

receiving hopper, intowhich the grab "discharges, the coal falls into the automatic -recording hopper weigher, from which it isdischarged on to the cross transfer belt con-veyor and is borne forward in the normalway. In the case of two other cranes a beltweigher is provided, arranged so that thetare weight of the empty belt is subtractedfrom the weight of the loaded belt. Inaddition to this apparatus, which measuresthe sea -borne coal received, weighers andrecorders are used in conjunction with eachof the gravity bucket conveyors. Thesemachines automatically record the totalamount of coal being handled.

A view of the boiler house at Barking.



LATHE WORKFOR

AMATEURS

Boring

By

H. DELLER

BORING OPERATIONSWHEN boring holes from the solid,

the work is first prepared bydrilling a pilot hole and enlarging

it to within reasonable limits of the sizerequired, before commencing the actualbaring. This is done by opening the holein steps by means of suitably sized drills.Where the hole can be roughed out beyond

turned to correct diameter in the holderand backed off to suit the material beingworked.

Boring a HoleAn alternative method is to use a front

cutter like that illustrated in Fig. 1, theside clearance being made sufficient to pre-vent rubbing. This type of tool is, however,

make sure that the heel of the tool willhave enough clearance. Where the toolshows a tendency to set up chattering, thetrouble can nearly always be overcome bynarrowing the nose of the tool to reduce thearea in contact with the work. It is mostnecessary to grind the tool to a fine shapewhen either the shank of the tool needs tobe small in proportion to the length, orwhen the job being bored is of a thincharacter.

The failure of a lathe to bore parallel isnearly always due to incorrect alignmentof the headstock spindle in relation to thetrack of the saddle. This is a fault that iseasily rectified where the headstock is aseparate casting, as jackscrews are mostlyprovided for adjustment, but in such caseswhere the headstock bearing housings arecast integral with, the bed, the remedy liesin the direction of careful bearing adjust-ment.

Mounting Work on the Face PlateWhere the work needs to be mounted on

the face plate, and particularly when an

Fig. 1.-Where the hole can be roughed out beyond the range of the largest drill Fig. 2.-Change wheels form a ready means of providing the necessary com-available a front cutter like that shown above can be utilised. pensation of balance.

the range of the largest drill available, acutter can be utilised for the purpose. Sucha cutter can be made with a mild steel shank,and several useful interchangeable hardenedsteel cutters will enable a drilled hole to beopened out rapidly for finishing by one or

unsuitable for" springiness."

To produce a good bored hole, it isessential that the cutting edge be rigid underworking Conditions. For this reason, selecta tool or bar that is as near to the maximum

deep roughing owing to angle plate is also used, it is most essentialthat the plate be balanced before com-mencing operations. Withdraw the drivingpin connecting the back -gear to the conepulley, so as to leave the mandrel free torotate in the bearings. The face plate will

Fig. 3.-Holes that are on the large size but of no great depth can be bored by Fig. 4.-Showing the finishing operations on the shaft of the Atom Minor describedmeans of a short bar mounted on the face plate. last month.

two boring cuts. The pilot.should be madean easy fit with about five -thousandths ofan inch clearance, in, say, i-in. diameterhole, and case hardened. A 90 degree pointon the locking screw engages with a counter-sink in the cutter. When making thecutters, the steel is cut off and the counter-sink made in the centre of the cutter blank,

size that the hole will admit, with sufficientallowance, of course, to permit the back ofthe bar to clear when the cut is removed.When an " Armstrong " type boring barand holder are used, the bar should beallowed to project as little as possiblebeyond the front face of the holder.

When setting the tool for centre height,

then come to rest with the heaviest pointat the bottom. Opposite to this point andnear the edge of the plate a counterweightis attached. Change wheels form a readymeans of providing the necessary com-pensation of balance as shown in Fig. 2.Failure to balance the mounted work causesthe lathe to run at an unsteady speed, a



condition from which an oval hole willresult.

Use of Pilot BushesFor holes that are deep in proportion to

diameter, and for which an ordinary boringtool would be too flimsy, use can be madeof a special form of bar which is supportedat the front end. The boring bar is made ofa length equal to about two and a half timesthe depth of the hole to be bored from astraight piece of finished material such assilver steel. A true bush, having a hole inwhich the bar is a running fit, is fitted intothe hole in the nose of the mandrel. Thesingle -point cutter in the bar is held by alocking screw and the distance that it issituated from the front end is such that the

A long hole is to be bored from the solidthrough a boss -like formation in a castinghaving a flat base. First mark out theposition of the hole centre on each end ofthe boss, suspend the casting between thelathe centres and pack up the base of thecasting level and clamp down. Drill ahole through the boss with a drill held inthe headstock and bore as described.

When boring a similar job with a coredhole, insert temporary hardwood endsinto the cored hole, and mark a circle oneach end of the casting concentric with thehole position. Remove the wood. and in-sert approximately the correct amount ofpacking beneath the base of the job andtest for correct position at each end of theboss with a bent scriber held in the cutter

the face plate. This will ensure that theangle plate is lying square without havingto use an indicator.

For boring operations the boring bar iscentred at each end and driven by means ofa carrier and the work fed on to the tool bythe sliding motion. Holes that are on thelarge size but of no great depth, such as inplate work, or bosses on long levers, maybe (by mounting the work on an angle plate),bored by means of a short bar mounted onthe face plate as in Fig. 3, or alternativelyheld in the chuck, for smaller bores).The foregoing remarks regarding cutteradjustment and floating cutters againappl-

Ifyinstead of fixing the bar direct to the

face plate, provision is made to attach it

Figs. 5 and 6.-Two further lathe operations dealing with the construction of the Atom Minor, described last month.

end of the bar enters into the bush beforethe cut comes on. The bar needs, of course,setting so that its axis coincides with thatof the lathe mandrel, and for this reason ismore easily mounted in a special block.Such a block can be made by clamping apiece of suitably sized square metal in thetool post and making -a reamed hole in itby means of tools held in the chuck. Aset -screw passing into the hole holds thebar. It will be apparent that the cut mustbe adjusted by moving the cutter in thebar either by tapping or by means of anadjusting screw.

Should a hole with a reamed finish bedesirable, the hole is bored a fewthousandths under size and finished witha floating cutter. Such a cutter is madedouble -sided, measuring the size of therequired hole over the cutting edges. Thecutter is not fixed in the bar but is left freeto float. On this account, therefore, thehole in the bar is made either square orrectangular, the tool sliding in with perfectfreedom but without slackness in anydirection. It must be mentioned thatprior to using such a cutter the hole mustbe bored true, as the original hole acts as theguide.

Boring Work held on the SaddleThe foregoing remarks have applied to

work that can conveniently be held in thechuck or on the face plate. Work of anawkward shape or when the lathe will notswing in the ordinary way, may often behandled by clamping to the saddle andoperating with a boring bar between thecentres. Provision is made on most centrelathes for doing this by means of Tee slotsin the saddle. With " American " typelathes it will be necessary to remove thecross slide and screw. The worst part ofthis class of work is the setting and, there-fore, a few instances of what are consideredthe easiest methods to e.nploy will follow.

hole in the boring bar, adjusting the castingaccordingly for height with packing, or bymovement crossways.

The third example deals with a job thatneeds to be bored through square with apreviously machined face. For the purposeof mounting, an angle bracket is required.To set the angle bracket square on thesaddle, lightly bolt it in position and bringthe vertical face to bear against the faceplate. Pass a bolt through a slot in theface plate and through a slot near enoughcentral in the angle plate, pulling the facestogether with a nut. Finally tighten theangle plate to the saddle and release from

to the top face of the tool slide, a sensitivetool adjustment will be obtained. By sub-stituting a front tool in place of the toolbar a machined surface surrounding thehole may be turned at the same setting.The cut is put on by running the latheslowly in back gear ani gving the feedhandle a portion of a turn each time itcomes round, or as is sometimes done forthe same purpose, a star wheel is attachedin place of the handle to engage with a pinon the bed or saddle of the lathe. It shouldbe pointed out that the slide is bolted flaton the face plate by the normal holding -down bolt holes.

TOOL GRINDING ANGLESThis Table should be used in conjunction with the article on " Tools and Tool Angles,"

which appeared on page 257 of our March, 1935, issue.

Material,

Tool -grinding Angles.Coolant

orLubricant.

Cutting Speed inFeetper Minute.

Clearance. Top-Rake.

Side.Rake.

CarbonSteel Tools.

High SpeedSteel Tools.

SourdsMild Steel . . 8-10 8-10 20 40 80

1 on )3% Nickel, Annealed . 8-8 5-8 10-12 Oil

oil20 45Tool1Tool Steel . . . 5-8 5 10 20 40

( Turps. )Grey Cast -Iron . . 6-8 5-8 10-12 Dry 30 60Hard Cast -Iron . . 5-8 2 5 Dry 10-15 30Hard Brass . . . 10-12 None None Dry 85 130Soft Brass . . . 8-10 5 15 Dry 45 80-90

Hard -drawn Copper . 8-10 5-8 15DryOr

Suds40 80

Aluminium . . 8-10 5-8 15-20Dryor

Paraffin80 160-180

Tool angles and cutting speeds may require modifying to suit conditions.To convert cutting speeds in feet per minute to revolutions per minute, find inches per minute by

multiplying given speed by 12, and divide by circumference of work in inches.


NEWNES PRACTICAL MECHANICS 351May, 1935

JUNCTION

Fig. I.-A simple experiment with copper Commencing Constructionand german silver wire. When connected as

MAKING ATHERMOPILE

heat produced by a singlemuscle twitch, and haveproved invaluable to phy-siology workers.

-.., shown and held in the flame of a candle the Start the work by---,..--,

mak-pointer of the galvanometer moves slightly. ing a small ebonite former

measuring about I in.IT is a well-known fact that when the long, i in. wide and f in. thick, and drill a

junction of two dissimilar metals is hole in either end for terminals or for assem-heated an E.M.F. is produced across the bly rods. Now pass the end of a length of

metals ; this effect is made use of in various No. 26 bare eureka wire through one hole, ortemperature -recording instruments and secure it to the terminal, wind about 20-25similar pieces of apparatus. Advantages of turns on the former, pulling it tightly, andthermopiles for commercial use are many,since they can be mounted in a convenientplace and the recording instruments groupedon a central panel. It must be rememberedthat the recorder is generally a sensi-tive milli -voltmeter, or moving coilgalvanometer ; the construction ofmoving -coil mirror galvanometers hasbeen described in this paper and theseare quite suitable for experimentalwork.

Those who are not familiar withCOPPERthe experiment should twist to- DEPOSITgether the ends of two short

pieces of copper and germansilver wire, connect the free ends to a sensi-tive galvanometer, and thejunction a deflection is noted (see Fig. 1).For general experimental purposes, a fairlysensitive instrument can be made from ashort length of eureka resistance wire, orgerman silver may be used. This type ofinstrument is used for general demonstra-tion purposes, especially when conductingexperiments on radiation, as, when carefullymade, it is capable of detecting the heatfrom a candle flame when held about 20 in.away. This is with a single element, butthe sensitivity can be increased by incor-porating several elements in the thermopile.It may be interesting to note that theseinstruments can be made of such a fine-ness, that they are capable of detecting the

TERMINAL

PACKINGPIECE

ASSEMBLING BOLT

Fig. 3.-Building up the elements.

Fig. 2.-Showing the construction of a single element.

keep each turn separate from itsneighbour. The finishing end issecured to the second terminal.When it is desired to build up aseveral element unit, the wireshould be anchored by forcingthrough small holes in the ebonite ;the elements are then assembled on longB.A. bolts with packing pieces in be-tween each pair. The various wires areall connected in series and the ends totwo bolts which serve as terminals. It isbetter to prepare each element completelybefore assembling (see Figs. 2 and 3).

The Plating BathBefore winding, the wire should be cleaned

bright with emery paper, since half of it hasto be copper -plated. A platingbath must be set up for deposit.ing copper, the solution consist-ing of copper sulphate crystalsand a little dilute sulphuricacid. In domestic measure thiswould be about one dessert.spoonful of copper sul-phate in three-quartersof a cupful of water towhich about 30 drops ofsulphuric acid are added ;stir only with a glass rod.To produce a copper -eureka junction, onlyhalf the wire is

plated, and to do this half the wire is placedin molten paraffin wax. Obtain a small flattin and melt paraffin wax into it to a depthof about in. ; now take the elements, andholding them with the long plane horizontal,carefully immerse in the wax until just halfis covered, remove and allow to set. Caremust be taken that the wax is not too hotor it will run up the wires where it is notneeded. It should be just molten so thatwhen the ebonite is dipped in it the waxsets on it immediately. Connect a wire toeach end of the eureka and then to thenegative terminal of a two -volt cell. Arheostat is connected to the positive ter-minal and to the anode of the plating bath ;immerse the element and adjust the currentuntil about 50 milliamps are flowing.Leave until a heavy deposit is obtained and

remove and wash carefully to remove anyacid. The wax is removed by placing thewhole in a beaker of water, and warming

TO GALVO

Fig. 5.-Showing the completed instrument suitablymounted on a wooden stand.

until the wax melts and rises to the surface.When cooled it can be lifted off in one cakeand the element removed from the beaker.It should then be dried with gentle heat andfilter papers (see Fig. 4).Testing Out

When the element is completed and con-nected to the meter a deflection should be

(Continued on page iii of Cover.)

COPPER SULPHATESOLUTION

Fig. 4.-Details of the plating bath.


352

An electric hairdrier which usesa z10-h.p. motor.

THE manufacture and production offractional-horse-power electric motorsis now an industry in itself. Whilst

the majority of these small motors are forworkshop industries, their employment forordinary household work is rapidly increas-ing. This does not mean the use of cumber-some machinery about the house, butportable electric motors, suitably encased,used as real labour-saving devices.

Manufacturers of these fractional-h.p.electric motors, faced with the problem ofdesigning a motor to suit the requirements ofalternating -current and direct -current users,have introduced a standard type of motor,known as the universal electric motor, tooperate efficiently with either source ofpower. This aims at standardisation, andrestricts the number of types of motors forthe same purpose, seeing that there is nonecessity for one motor for A.C. and anothermotor for D.C. On the other hand, theconsumer, in the event of moving toanother part of the town or country wherethe supply is different, need have no fearof his electrical apparatus being useless.

It is this type of motor, the universalmotor, designed to operate on the standardelectric supplies of 200/250 D.C. and200/250 volts A.C., 50 cycles, which, in themajority of cases, is used for all domesticmotor appliances.

It is a type known as the series -com-mutator motor, and, besides its inter-changeability between A.C. and D.C.supplies, its chief characteristic is its widerange of speed variation depending on itsload, and its suitable starting torque for theapplications mentioned below.

A 55 -hop. motor which is now extensivelyused for television receivers.

NEWNES PRACTICAL MECHANICS May, 1935

INSTALLING DOMESTICThe employment of fractional -horse -power electric

and these motors have been incorporated

The Vacuum CleanerPerhaps the chief application of the

fractional -horse -power electric motor inthe home is the electric vacuum cleaner.Cleaning by this method is effected by thesuction of air either through the materialto be cleaned or over its surface, and thecollection of dust and dirt in a container(usually a canvas bag) fitted in or to theapparatus.

The suction is produced by a fan, drivenby the motor and revolving at high speed.The fan can be used for blowing instead offor suction when necessary.

In one of the most popular types ofvacuum cleaner the motor and fan arehoused in a polished aluminium case, oneend of which forms a nozzle to work alongthe floor, as shown in the illustration,the whole apparatus being fitted with anunder -carriage of wheels or runners for easymovement along the carpet or other articleto be cleaned. Attached to the case is atrunnion -mounted pole, with shock -proofhandle containing the trigger or rotaryswitch to control the motor, the connectionto the supply mains being made through theusual flexible cord (a few yards long) to thewall -plug or lamp adapter.

When the nozzle of the aluminium casingis not required, provision is made for theattachment of a flexible hose throughwhich the air is drawn, and to the ends ofthis hose can be attached adjustableaccessories for various cleaning and brush-ing purposes. In this particular type ofcleaner, ball bearings are fitted through-out.A Floor Polisher

The electric floor polisher, which is similarin constructional features to the cleaner,is used mostly for floors, linoleum andstaircases. It consists of a motor mountedvertically and geared to one or morebrushes of horse hair or other suitablematerial. When two brushes are employed,they revolve in opposite directions, asillustrated. In this type of polisher twosets of brushes, mounted on a circular plate,are supplied, one set for spreading the waxand the other for polishing.

The switch mechanism is usually con-trolled by a movement of the pole or handle,and operates automatically on the motorcasing which embodies a switch.

An Electric FanThere are two types of electric fan for

domestic use, namely, the exhaust orventilating fan and the table fan. Theformer is used mainly for large kitchens,whilst the table fan is the popular type for

14111kinammusigri(Left) A vacuum cleaner which is driven by a PA.p,motor, and (right) a floor polisher which uses a

similar type of motor.

use in the average home. This type of fan,if placed close to a suitable air inlet, say anopen window, changes the air of a rocm.Some of these fans have an oscillatingmovement, the fan turning from side toside through an angle of about 100 degrees,whilst some fans move up and down. Theseadditional movements cause au air disturb-ance over a wide area and create lessdraught than the fan mounted on a fixedcasing. In construction, the fixed modelconsists of a universal motor in a lightcast-iron casing, with metal or mouldedblades about 10 in. from tip to tip, suitablyguarded, attached to the end of the motorshaft. The motor is mounted to a standfitted with a tilting movement, so arrangedthat it can be operated as a table fan or abracket fan. Fitted in the base of the standis a regulator which provides an " off "position and two speeds. Where higher -powered fans and oscillating movements are



ELECTRICAL DEVICESmotors for household work is rapidly increasing,

in a number of labour-saving devices.

employed, it is usual to fit either an A.C. ora D.C. motor.A Hair Drier

The electric hair drier consists of auniversal motor mounted in a Bakelitemoulded case fitted with a shockproofhandle, such a handle being necessarybecause the hair drier may often be usedwhilst held in a warm, moist hand.

The casing contains, besides the motor,an electric heating element. The motorrotates a small fan which draws in air andexpels it through a tube or nozzle (part ofthe casing) in which the heater element islocated, thus producing a blast of warm air.The switch is fitted in the handle andcontrols both motor and heater separately,so that hot or cold air may be obtained asrequired.The Gramophone Motor

The universal motor supplied for rotatingthe turntable of the gramophone is fittedunderneath a top plate and below theturntable. As the motor is out of reach andsight of the operator, it is usually of theunprotected type.

The natural high speed of the motor ismechanically controlled, and by a centri-fugal system of sprung weights fitted to themotor shaft the speed is governed andmaintained at about 2,000 revolutions perminute. The motor shaft engages throughsilent reduction gearing with a verticalshaft carrying the turntable, the resultantspeed of this shaft being about 100 revolu-tions per minute. This speed is adjustedto the required 78 revolutions per minuteby a brake pad engagement controlled by alever projecting just outside the edge of theturntable.

In the type illustrated an automaticstart and stop mechanism is fitted under-neath the turntable and controlled by themovement of the pick-up arm. When thepick-up arm is resting away from the record(its normal non-playing position), theswitch for the motor is " open' and the

A very compact gramophone turntable unit driven byan electric motor.

action of bringing the arm to the edge ofthe record for playing automatically closesthe switch and starts the motor. When thearm has reached the playing end of therecord, the mechanism automatically opensthe switch and the motor stops again.

Television MotorIn television apparatus the universal

motor is used for driving the scanning disc,mirror drum, mirror screw or other form of

exploring device. The normal speed for atelevision drive to suit the present trans-mission is 750 revolutions per minute, whichis too slow for the natural speed of themotor. The speed is controlled by varyingthe voltage applied to the motor, this beingeffected by including a variable resistancein series with the motor. For televisionpurposes the motor (open type) has to bedesigned to run with an absence of noiseand mechanical vibration.

Consumption of ApparatusThe consumption of electricity by the

applications of fractional - horse - powermotors outlined above is so low that theycan all be safely attached to the lightingcircuit if the consumer has not got a powerpoint. In the accompanying table usefuldata concerning these motors is tabulated.

The number of hours' use for a penny is

An underneath view of the floor polisher, showing therotation of the brushes.

based upon the general power charge ofld. per unit.

Type Approx.con-H.P.

Watts

Burned

Hours ofuse fora Penny

Vacuum cleaner .Floor polisher .Fixed fan .

Hair drier . .Gramophone motor.Television motor .

**

.217

pr*Ti.h

200200

40650

1040

55

254100

25

An electric fan which employs a h-h.p. motor.

It should.be noted that in the case of thehair drier consuming 650 watts, 600 wattsis taken by the heating element, onlyabout 40 or 50 watts being taken by themotor.

RefrigeratorsAt the foot of the column is illustrated

a sewing machine adapted to work froman electric motor instead of by the in-finitely more cumbersome treadle arrange-ment, whereby inexpert users may easilyreverse the mechanism. Similarly, thereare mincing machines fitted with electricmotors which form a handy labour-savingdevice. There are also electric refrigeratorswhich contain small motors whereby variouschemicals are made to obey certain physicallaws of evaporation resulting in the produc-tion of cold. It is interesting to note thatby the production of heat in one part of thesystem the production of cold is set up inanother. Whereas vacuum cleaners arenow extensively used in this country,refrigerators are comparatively rare, largely

due to our equ-able climate.That they arerapidly cominginto popularfavour, however,is borne out byproductionfigures of theleading com-panies.

The general utility of the motor is again shown in theabove photograph, where it is used to drive a sewing

machine.



SCALE MODELAIRCRAFTNo. 4

THE S.E.5A was one of the mostsuccessful machines of the single -seater fighter class built during the

war and was flown by most of the successfulpilots. Ball, McCudden, Bishop, McElroy,Janes, and a host of others used it, and amodel of this machine has a historical aswell as a constructional interest.

If you have built the other models inthis series you will have little difficulty inconstructing the S.E.5A, although there area few additional parts which are smallerthan in the previous models, but whichshould be added to create a real likeness.

Below is given the list of parts and thesizes in inches of the pieces of wood fromwhich they are shaped. The length columnindicates the run of the grain.

LIST OF PARTS

RadiatorFuselage . . . .Valve Covers -two .Exhaust Pipes -twoHead Rest . .

Tall Piece and RudderStabilising Fin .Tail Skid . . .

Elevators -two

Long.0.754.150.552.20.71.00.850.251.25

Wide.0.50.50.10.150.351.00-250.20.8

Thick.0.1250.750.07500750.1250.050.05Q-050.05

Top Wings. Outer Sec-tions -two . . . 2.6 1.1 0.1

Top Wings. Centre Section 1.2 1.1 0.1Bottom Wings -two. . 1.0 0.1 0.05Outer Interplane Struts -

four . 1.25 0-1 0.05Under -carriage Struts -

four . . . . 1.25 0-15 0.05Axle . . . . 0.9 0-05 0-05Propeller. . . . 1.8 0.2 0-1Wheels . . 0.45 dia. 0.1Shock Absorbers . . 0.1 04 dia.Vickers Gun . . . 0.5 0.1 dia.Lewis Gun }See Text.Aldis Sight

Side, plan and frontviews of the model.

=11,111 111

SCALE-OVIODEL

S.E.5AThis month we deal with the constructionof a single -seater fighting machine thatwas used extensively during the Great War.

A photographof the finished

model.''See Special Competitionon page 370.

Commence by shaping the radiator,which is very similar to an old -type carradiator; in fact, cAr radiators were actuallyused. The tubes can be imitated by filingrows of slots across the face, or if moredetail is required, short lengths of bare wirecan be glued across from side to side. Theradiator can then be fixed with two pinsto the piece of wood to be used for thefuselage, where it will act as a guide forthe correct shaping of the fuselage. It neednot be glued in position until after thefuselage is finished. The fuselage is prac-tically square from the nose up to thefront edge of the cock -pit, and from thereit is tapered on all sides to the tail unit.The head rest should be first glued as anoblong block to a small flat, filed in the topof the fuselage, and later shaped away and

Scale

faired into the sides of the fuselage. Thecock -pit should be gouged out to some littledepth, a fairly large hole drilled in thecentre making the cutting away to shapemore easy.

Also drill the four holes to carry theinside interplane struts which are justinside the exhaust pipe positions. Nextcut and shape the exhaust pipes andthe valve covers and glue them to thefuselage. The Vickers gun is fluted with afile and has a pin inserted into the end toimitate a barrel. This is glued to the portside of the top of the fuselage. The Aldissight is a piece of 14 S.W.G. wire solderedto two cut-off pins which is pressed intothe top of the fuselage. Now cut and shapethe tail unit, glue it in position, and fix theelevators ; it being better to pass a pinthrough the fuselage to give them addi-tional support. The hinges of the rudderand elevators can be scored or separated,and fitted with hinges and thin pins.The Top Wing

Next shape the top wing centre sectionand the struts, glue them into position, andallow to set hard before fitting the wings.

The upper and lower sets of wings arebest mounted together, with the inter -plane struts glued in position between ablock of wood of the correct thickness.Pins with the heads cut off are inserted

into the ends of tlie wings, and whenthe wings are properly set, removethe block of wood, and glue andtransfer to the correct position onthe machine.

The Lewis gun mounting is astrip of 22 S.W.G. brass or alumin-ium 0.075 wide, formed into an archand mounted on two small blocks ofwood on the top plane with thelower end divided in two andbrought down to the top of thefuselage on either side of the rearend of the Aldis sight. The Lewisgun on the machine shown in thephotograph is carved from woodwith a pin inserted for the barreland a thick fibre washer glued ontop for the ammunition drum.

S.E.5A's are painted a darkgreen -brown, with the usual identi-fication discs on each wing tip andthe sides of the fuselage, andtricolour strips on the rudder.Occasionally individuals paintedtheir machines in different coloursor carried distinguishing marksother than official, but these effortswere- eventually forbidden by theauthorities.

4" 2 3 4s


May, 1935 NEWNES PRACTICAL MECHANICS 35S

TELEVISION MADE EASY_PART IIIBy H. J. BARTON CHAPPLE, Wh.Sch., B.Sc.(Hons.), A.C.G.I., D.I.C., A.M.I.E.E.

This month we deal with an ingenious piece of apparatus called the Iconoscope, which may be likened to the eye,for in effect It has a retina, lens, rods and cones, together with nerves which lead to the " brain " of the device.

ATHOUGH methods for scanningscenes to be televised at the trans-mitting end which avoid any form of

mechanically rotating or oscillating devicehave been known and worked on for someyears, it is only of comparatively recentdate, synchronising almost entirely withhigh - definition tele-vision work, that theseschemes have comeinto prominence. Inone way or anotherthey harness and con-trol the movements ofelectrons either as ahigh velocity streamor as an ordered massassembly, as in thecase of what has beentermed an " electronpicture."

Nature of ElectronsIt is as well to

remind readers thatelectrons are reallyextremely minute par-ticles of negative elec-tricity. They can be

result of light stimula-tion on photo -electricsurfaces or by render-ing a filament (cathodeelectrode) incandescentby passing a currentthrough it and " col-lecting " the electronswhich escape from thesurface tension andbecome free, in muchthe same way as watervapour is evaporatedfrom the surface of theliquid. Owing to theirelectrically negativecharacteristics, and the fact that to allintents and purposes they are withoutinertia, they can be influenced very readilythrough the agency of electrostatic orelectromagnetic fields produced in theorthodox manner.

Again, when required, their presence ormovement can be made visible to the eyeby allowing them to impinge at high velo-city on screens covered with a thin layer offluorescent material. At their point orpoints of impact on the screen a small orlarge area of fluorescence occurs, and, as weshall see later, this property is put to goodservice for the purpose of building up atelevision picture in terms of light and shadeat the receiving end.

An Early WorkerOne of the first pioneers to show really

demonstrable pictures using electronicscanning was von Ardenne of Germany. Hewas a firm advocate of what has come to beknown as variable velocity modulation,whereby television pictures were scannedand later reproduced at the receiving endthrough the agency of an electron beam ofconstant intensity, but whose rate of travelin a horizontal plane was varied in accord-

ance with light intensity. That is to say,the bright portions of a picture on a fluor-escent screen would be due to a relativelyslow velocity, whereby at the points ofimpact there was sufficient time for thefluorescence to be extremely intense andbrilliant. On the other hand, at the dark

Fig. 1.-Some of the early equipment used by von Ardenne to transmit television picturesby using a cathode-ray tube scanner.

sections of the picture the velocity of theelectron trace would be made so high thatthe measure of fluorescent glow would becorrespondingly reduced, and so on inter-mediately.

MOSAIC SCREEN

Unfortunately, the apparatus designedby von Ardenne was only suitable for thetransmission of standard talking films (orstill pictures such as lantern slides), whereasmodern electronic devices include bothfilms and ordinary exterior or interiorscenes within the scope of the scanner. In

Fig. 1 is shown a viewof some of the earlyequipment used by vonArdenne in his experi-mental work withstills. An opticalimage of each filmpicture or still wasfocused on to the largeend of the cathode-ray tube, and the lightvariations produced bythe focused electronbeam spot as it ex-plored this picturewere made to activatethe electrode surfaceof a solitary photo-electric cell mounted,in the case of Fig. 1,in the rectangular boxto the left-hand sideof the amplifier. Thevarying voltage outputfrom this cell and asso-ciated amplifier werefed to the transmitterin the normal mannerfor transference tothe receiving end byradio.

Simulating the EyeReverting now to

the electronic scannerscovering a variety ofanimate and inanimatesubjects for trans-mission, a particularly

interesting example is the Iconoscope deve-loped originally by Zworykin in America.This ingenious apparatus may be likened tothe eye, for in effect it has a retina, lens,rods and cones, together with nerves which

MAGNETICDEFLECTINGCOILS

CATHODE RAY TUBE

Fig. 2.-The Iconoscope developed originally by Zworykin.



lead to the " brain " of the device. Itsshape and assembly can be gathered by areference to the simple diagram Fig. 2.First of all there is an evacuated glasschamber in the spherical section of whichis accommodated a sheet of mica, which inthe original models was about 4 in. square.This is the equivalent of the eye retina, foron the face of this sheet is chemically con-structed a mosaic of millions of very minutephoto -electric cells said to be built up froma caesium base. Backing this sheet of mica,which itself is some thousandths of an inchthick, is a silver deposit, so that, as a whole,the assembly is, in effect, an arrangementof an enormous number of separate andA

C

Fig. 3.-The zig-zag line traced on the mosaicscreen. Strictly speaking, the normal line traverse

is inclined and the fly -back stroke horizontal.

distinct condensers, with the added advan-tage that the mosaic surface is photo -elec-trically sensitive.

A good quality photographic lens com-bination focuses sharply and clearly on tothis mosaic surface an optical image of thescene it is intended to transmit, whetherthis be from a film, an interior studio studyor an effect in the open air. This lightstimulation over the whole surface causeseach individual but tiny photo -electric cellto acquire an electronic charge in directproportion to the degree or amount ofpicture light which it receives, and this isimparted to its inherent condenser. Fromthis " ele4rical memory " picture so formedmust be cit ated the television signal in anordered line sequence of equivalent varia-tions, and to effect this the second part ofthe equipment within the whole bulbassembly is brought into play.Cathode-ray Scanning

This is really a standard form of cathode-ray tube having an incandescent cathodefrom which is emitted electrons. These areformed into a stream through the agency ofthe normal type of focusing device andaccelerated forward at high speed byapplying a high -positive potential to aneighbouring circular anode having a smallaperture through which the electrons aredirected. This beam is directed on to theplate mosaic, and to give the beam itsmethodical scanning action two pairs ofcoils (seen to the rear of Fig. 2) are mountedin a framework and placed over the tubeneck. Through these coils are passedsimilar types of saw -tooth currents, buttheir frequencies are quite different. Thesaw -tooth current is so named because ithas a steadily increasing value with time,and after reaching a certain maximum valueit drops almost instantaneously to itsoriginal low value.

Producing the SignalSince the beam passes right through the

magnetic field produced by each pair ofcoils it is made to alter its direction inaccordance with the strength of each field.One pair of coils causes the beam to movehorizontally at a constant speed in onedirection across the face and then " flyback " to the other side, repeating thisaction at the frequency with which the saw -tooth pulses occur, which, in actual fact, isthe line repetitive frequency. In the caseof a 240 -line picture reproduced at twenty-five pictures per second, this frequencywould be 6,000 per second. The pair ofcoils producing vertical deflection haspassed through them a saw -tooth wavepulse at the picture repetition frequency,and it is therefore easy to see that the com-bined result of this dual magnetic deflectionof the beam is to make it trace a path acrossthe mosaic face in a series of zig-zag lines,somewhat as shown in exaggerated form inFig. 3.

The passage of the beam across eachindividual charged condenser causes eachunit to discharge itself in turn, and theseresulting currents are fed to an amplifierand constitute the television signal, beingat every instant proportional in its stage ofconversion to the separate and distinctlight values of the original scene beingtelevised. Another factor to be noticed inconnection with the wholly electrical deviceis that once each separate photo -electric cellcondenser unit has been discharged and pro-duced its quota of signals, it immediatelycomes under the optical picture influenceagain and commences to build up anotherelectrical charge in proportion to the picturelight to which it is exposed.

Another DeviceAnother important electronic scanning

device works on rather a different principle,employing for this purpose an image dis-sector tube. This is simply an evacuatedcylindrical glass tube in which at one endis a circular cathode surface covered with auniform layer of an extremely sensitivephoto -electric material. Using the normalform of photographic lens, an optical imageof the scene to be televised, whatever itsnature or type, is focused on to this sureface. This has the effect of producing imme-diately a form of electronic discharge, thecross-section of each minute portion ofwhich corresponds exactly in intensity tothe picture light which is incident upon it,and which, of course, originated the 'dis-charge. Such an en manse discharge ofelectrons from the cathode surface is calledan electron image, and under the influenceof an accelerating positive potential thiselectron image is drawn forward bodily.

No matter how carefully the tube andcathode surface is constructed, once theelectron image has left this surface it failsto keep its original formation unless stepsare taken to retain the electron focus.This is brought about by surrounding thetube with a solenoidal coil through which ispassed a steady current. This creates auniform magnetic field, and by a carefuladjustment of the coil constants and currentvalue it is possible to ensure that the elec-

tron image, after it has moved forward to aposition XY in Fig. 4, is exactly in focus.If this was not so, the picture that wouldbe seen at this point, assuming that afluorescent screen rendered it visible, wouldbe blurred and, if badly maltreated, electric.ally quite unintelligible..A Dual Scanning Movement

In the plane XY is what is termed ananode target, that is a surface in which is asmall aperture whose size is governed bythe electron image area emitted from thecathode and the degree of line dissectioninto which it is intended to split up thepicture for conversion to a television signal.Instead of moving the aperture over theimage, the image is made to move over theaperture, which, under these circumstances,is quite steady. Since the en masse electronimage has, of course, a negative electricalcharacteristic, it is readily influenced bythe effects of magnetic fields. As in the caseof the Iconoscope, therefore, two pairs ofmutually perpendicular magnetic fields areproduced through the medium of four coilsarranged at right angles to one another andworking as two pairs.

One pair of coils produces the horizontaldisplacement due to a high -frequency saw -tooth current being fed through them, whilethe second pair is instrumental in givingthe vertical movement by applying to ita low -frequency saw -tooth current. Thecombination of the two varying magneticfields sweeps the electron image across theaperture so that the electrons pass throughas a stream of varying density formationcorresponding to the original light intensitypicture, but line dissected.

This continuous but varying strengthelectron current constitutes the televisionsignal, and after amplification it is passedto the radio transmitter to modulate thegenerated carrier wave for propagation *ntospace as an electro-magnetic wave. X

FOCUSSING COIL.0000000000000000

APERTUREDTARGET

0000000000000000CATHODE

Fig. 4.-The bare details of an image dissector tube.

When either of these electronic scanningdevices are employed for transmittingordinary talking films, one pair of deflectingcoils can be dispensed with, since the down-ward motion of the separate film picturesthrough the projector provides this. Irre-spective of this, however, the scanners pro-vide a most ingenious way of producing thenecessary television signals by wholly elec-trical methods, and concentrated effort isbeing made in developing them to a highdegree of efficiency.

MESSRS. WHITELEY ELEC-TRICAL RADIO CO., the well-known loudspeaker manufacturers,

will soon be manufacturing televisionreceivers and component parts at theirVictoria Street factory.

This side of the business will be handledby the formation of a new company under

A NEW TELEVISION COMPANY

the title of the Whiteley Television Co.Ltd., with a nominal capital of £1,000.

Mr. A. H. Whiteley, head of the firm,stated that so far only experimental work

confined to research has been carried out." The new company," he said, " has been setup so that as soon as an efficient televisionservice becomes definitely established, weshall be in a position to put receivers andcomponents on the market. We anticipatethat the first demand will be in the way ofhome -constructed sets."



The Davis turbine-an alternativeprime mover.

THE woodwork is almost completed,the stern tube fitted, and now is thetime to fit the rudder tube. It is

advisable to spend a little extra care onthis job, for I have noticed that this is thejoint where leaks very often occur. Drill ahole in the hull as marked on the plan, anddrive the tube in, until nearly flush under-neath the hull. Unlike the stern tube, thisrudder tube must fit tightly into the holeso that the joint is water -tight.

The hull also must be made water -tight,ready for its finishing coat of enamel, andrequires three or four layers of under-coating, inside and out, to ensure this. Youmust remember that when Streamlinia setsher stern down to a 50 -yd. run she is goingto churn up considerable spray, and if thisfinds its way to any exposed wood, offcomes the expensive enamel.

I find it a good idea at the end of anevening's work to give the hull a thin coatof lead paint, inside and out. This will savedelay later, when the rest of the boat iscompleted.

The EngineIn deciding on the machinery of Stream-

linia, the main consideration was a reallyefficient plant at a moderate outlay. Thehull, of course, is quite capable of carryinga flash steam set, so if any of you wish tomake a " record -breaker, the hull anddesign of this boat are ideal. Streamliniahas been tested fitted with a twin enginewith a 60 -lb. pressure, and the resultwas amazing. The engine used was theG.F. Twin -Cylinder Steam Engine manu-factured by Bassett-Lowke Ltd., and aspecial " de luxe" model of Streamliniacontaining this engine will be marketedin the near future.

For the purpose of this model, the enginechosen was the Stuart " Meteor " High-speed Marine Engine. It is inexpensiveand really efficient, and has the addedvirtue of interchangeable parts.

Some readers may be surprised that theengine is set at an angle to line up with thepropeller shaft, but this does away with theneed for a universal joint inside the hull, andreally does not affect the working of theengine, as the displacement lubricator dealsefficiently with all cylinder oiling.

The Boiler and LampThe other parts of the steam set are the

boiler and the lamp. The boiler is ofbrazed copper tube, tested to a full capacityof 60 -lb. steam pressure. The methylatedspirit lamp is of the new Harrison design,

Machinery for"Streamlinia"

The making of Streamlinia is almost completed, and now readers shouldbe able to visualise the finished model, which will be well worthy of the

effort and work that has been expended on it.

produced by Bassett-Lowke Ltd. It hasbeen evolved after much research, and dis-places the old sardine -tin type of lamp,which is so unreliable, as one never knowshow much spirit to put in, and the resultis either a short run or a dry boiler. But

SPECIAL COMPETITIONWe offer the following prizes for the best

photographs of models of Streamlinia builtfrom the designs published in this series.Readers who have not yet started to build thisfine speed -boat should do so without delay.Messrs. Bassett-Lowke Ltd., of Northampton,who supply the parts and the mechanism forit, have generously added £3 3s. to the prizelist.

RULES1. Models must be made from the designs

published in these pages, and from the partsspecified.

2. It is only necessary to send a photographof the model, and this must bear the nameand address of the sender.

3. The Editor's decision is final and anexpressed condition of entry.

4. Stamps must be enclosed for return ofthe photographs.

5. All photographs must reach us not laterthan June 10th, 1935.

6. The Judges will be Mr. W. J. Bassett-Lowke and Mr. F. J. Camm.

7. Prizes will be awarded for the best -finished model.

PRIZESFirst Prize : £3 3 0Second Prize : £2 2 0Third Prize : £1 1 0

100 Consolation Prizes of Books to be selectedby the winners.

this new lamp has been designed to boilercapacity and is safe and efficient in all con-ditions. It is run on what is known as theautomatic or " chick " feed principle, anddoes not allow more spirit to go to theburners than they can consume.

The complete set can be obtained, readyto mount in the hull, from Bassett-LowkeLtd.

It is advisable to get acquainted with thesteam set before fitting it into the hull,so take out the spirit container, draw thelamp out of the fire -box, and examine thisthoroughly. Notice particularly how thewicks are put in, as later on, when newwicks have to be fitted, it is useful to knowhow tight to fit them. They should not beloose, as they are liable to blow out whenthe lamp gets hot.

Now we can proceed to give the set a" bench " test.

To fill the boiler, unscrew the safetyvalve, which is situated near the funnel,and with the measure and funnel suppliedpour in seven measures of water. Replacethe safety -valve cap and screw downtightly.

Then, being sure that the control is closed(the lever should be right down), fill thespirit container with best -quality methy-lated spirit. It is best to buy this from areliable chemist, as some of the cheapergrades of spirit do not give off anything likeso much heat, and so little is needed thatprice is not an important factor. Replacethe container, being certain that thepipes are inside the lamp reservoir, pull thecontrol lever right up, and wait for a few

Showing the plant placed in the hull of - Streamlinia" in the correct position.



The hull ready for fining in the steam plant with falsefloor and stem tube.

minutes to allow the wicks to saturate, thenlight these with the igniter supplied.

Oil the Parts wellWhile steam is being generated, see that

the engine is well oiled (use Rocket MachineOil for all working parts) and fill up thedisplacement lubricator situated betweenthe throttle control and cylinder withRocket Cylinder Oil. Keep a close watchon the pressure gauge, and when it registersbetween 30-40 lb. open the throttle andrevolve the flywheel a few times. This willfree the engine of condensation. Let theplant run steadily for a few moments whenthe pressure has reached 55. It is usefulto test the best throttle position. Rememberthat an engine which is racing is not alwaysdoing its best, and this bench test isinteresting because each part can be seen

doing its work, and you can easily make anynecessary Adjustments.

After this you can proceed to fit theplant into the hull. Fit the false floor inand set the plant in its correct position.Now we resort to the testing tank or bath.Put the hull in the water, and be sure that itfloats at the correct water level. This ismost important, as the steam plant mustincline slightly aft to ensure the flow of thespirit. The tray should be about f in.lower aft than forward. This can be ascer-tained with a spirit level, or, more simply,by pouring a drop of water into the tray,afterwards carefully drying it out.

Take the hull out of the water and screwthe plant down with the screws provided,seeing that the shaft coupling is quite freeand revolves easily. The exhaust pipe isnext fitted. This is quite a simple job. Itis put out at the stern, as the boiler doesnot need a forced draught, and it gives the

beautifully balanced job and does notrequire any resetting, and gives the mostconsistent performances over a number ofspeeds.

Testing outNow comes the great moment-a test on

open water. Choose if possible a calm day,as with an open hull a high wind is likely toblow out the lamp. Give the boat severalgood runs and make notes of her per-formance, such as time of raising steam,and running time after steam up. Noteespecially how much water is left in theboiler when the spirit container is dry, asthis will need deducting from the nextfilling.

Further experiments have been carriedout, using the Davis Steam Turbine, whichgave good results. The Impulse Multi -Velocity Turbine consists of rotor, casingand nozzle. The rotor used for this boat is

The complete engine set, with the Stuart " Meteor" engide mounted ready for fitting.

boat a better appearance, besides forcingany engine priming right clear of theboat. Next fit on the propeller. This wefound a difficult part to choose. Mostmodel enthusiasts fit a two blade, and pro-pellers of this type were tried with the usualvarying results, but eventually we chose a2 -in. three -blade " Remod." This is a

2 in. in diameter and requires from 60 to80 lb. pressure to drive a metre -size boat.It can be obtained, complete with frictionreduction gear, jet and union, from Bassett-Lowke Ltd. This prime mover can befitted to the boiler, and the only alterationnecessary is a longer propeller shaft, whichcan be supplied to order.

MORE than 100,000 people havealready seen the photographic exhibi-tion, " Flying Over the )mpire,"

which has been arranged by ImperialAirways, and the interest of which hasbeen enhanced by a remarkable collectionof infra -red photographs taken by a Timesphotographer during an air voyage over theEmpire routes and lent for exhibition bythe proprietors of that paper. After aninaugural display in London last July-theopening ceremony being performed by theUnder -Secretary of State for Air-thispictorial air pageant went on tour through-out the country, being shown in most ofthe important provincial cities. Actually,three of these exhibitions are now touringin the British Isles, while one has gone outto Australia, and another is being stagedin Canada with the support of the Cana-dian National Council of Education. AtOttawa the exhibition was arranged inthe main hall of the Nktional Museum,nearly 1,000 people attending the open-ing ceremony. The Exhibition has alsovisited Montreal, so as to coincide with theannual conference on flying which was heldthere.

A PAGEANT IN PICTURES

What it MeansIn the minds of spectators, as they move

from picture to picture in the wonderfulcollections that have been assembled,comes a realisation of what it means tooperate-as Imperial Airways and theirassociated companies are now doing-regular services by air over a total distanceof approximately 20,000 miles. One sees agreat 4-engined air -liner leaving the Londonairport on the first stages of an air journeyacross the Empire. Paris appears below.Europe is left behind. You see a big flying -boat winging its way above the Mediter-ranean, with all those coastal and islandbeauties which are viewed to such advantagefrom the air. Then comes Egypt, with itspyramids and golden sands. On you fly, infancy, over the desert to Baghdad. with thegold -covered minarets of the El-Khadimainmosque gleaming in the brilliant sun.After which you catch a fascinating glimpseof that marvellous Arch of Ctesiphen, relic

of the Palace of the Parthian Kings. On,devouring distance, above the Persian Gulfwith its Sheikhs, pearl -fishers and camels-on to Gwadar, Karachi, and further east-ward along the great route which nowcarries mails for nearly 13,000 miles fromLondon to Brisbane in Australia.

Over AfricaParticularly fascinating are one's pic-

torial impressions of a flight over Africa.The desert lies beneath. You approach thebig -game lands, looking down on elephantsand other animals of the wild from a bird's-eye point of view. Hills, mountains androlling plains alternate with forests, lakesand rivers. It is the pageant of a mightyContinent that passes before your eyes. Inaddition to this pageant in pictures of thegreat trunk air -lines, one is shown photo-graphs of the saloons and control -cabins ofmodern air -liners ; of the engines whichdrive them so smoothly along the highwaysof the sky ; and of the airports, wirelessand meteorological equipment which nowenable our British air -liners to fly with anall -the -year round reliability of just on100 per -cent.



HOME plumbing seldom attracts theamateur mechanic as does wireless -setconstruction or model making, and

yet what more useful " handyman " thanone who can repair and " service " house-hold sinks, bath, pipes and traps ? Thetools required are to be found in mostdomestic tool -boxes. The additions are arubber force cup (18.) ; a length of draincane (6d.) ; a coiled wire trap cleaner (9d.) ;tow ; tallow ; and washers. The possessionof a shifting spanner, pipe wrench, and gaspliers is assumed.

Re-washering TapsIn addition to the fact that few noises

are more irritating, wastage due to leak-ing taps is liable to be detected by aninspector of your water company, with anaccompanying fine. Choose a time of dayfor your repair when turning -off the waterat the main will not be a source of familycomplaint.

Taps leak because the " washer " isworn out. New washers in leather orrubber cost ld., and fixing a new one is

HOUSEHOLD PLUMBINGHINTS

Home Service for Sinks, Bath, Pipes and Traps

easy. First find the main stop tap on thehouse supply and turn it off. Open thetap you are going to re -washer, and whenthe water has ceased to flow-and notbefore-use your wrench and undo the bodyof the tap. Don't make a mistake andloosen the tap itself off the supply pipe. Itis the big nut below the tap spindle whichmust be unscrewed. The tap will now bein half and you must get at the " jumper."

This may be in the top half of the tap ormay be resting on the seat in the body.Remove it with your fingers and loosenthe tiny nut which holds the washer on itsstem. Replace with a new washer andtighten the little nut. After putting thetap together again, turn on at the main cock.The tap should turn off easily withouteffort and without 'dripping. In frostyweather taps and pipes will freeze, but the

big water companies everywherenowadays specify heavy gaugelead pipes which seldom, if ever,burst. They recommend thatthe water be turned off at themain at night, and that frozensections of pipe be thawed withrags soaked in boiling water.The lead service pipe from the

main cock to the supply tankis sometimes an exposed pipe.

If that is the case, it should

(Above) Turning the wateroff at the main, and (Right)removing the tap nut with ashifting spanner to get at the" jumper." This is where the

new washer is inserted.

On the left is shown the method of connecting thepipe to supply water for the basin shown above.An amateur fitted this basin in a week -end at a

total cost of £5 18s.

be wrapped spirally with strip felt andtightly bound with string.

A Blocked SinkOne of the household appliances most

likely to become stopped up is the sink.There are three causes of stoppage : (1) solidmatter in the lead trap under the sink ;(2) some solid such as congealed fat whichhas passed through the trap but hasjammed in the lead waste pipe ; (3) outsidegully, or syphon trap, blocked with vegetablerefuse, soap and fat.

First use the rubber force cup. If thesink is not empty, bale it dry, fill it withhot water and work the cup vigorously.If the stoppage will not pass away in fiveminutes, it is not likely to yield to thesemethods, and the trap must be opened.In the bottom of the bend is a brass plugwhich you must now unscrew with thepliers, but have a bucket ready beforeunscrewing the plug. Turn on the hot tapand you will probably find the obstructionwill come away, especially if you work theforce cup, or use a long thin wire or coiledwire drain cleaner through the hole. Thewaste pipe is now probably free, and youshould replace the plug and fill the sinkwith hot water. If it does not flow awayeasily when you remove the stopper, thelead waste pipe is blocked on the outletside of the trap.

This is where the cane comes in. Nowfind the outlet of the pipe. This generallydischarges into what is called a " gully,"which you will find probably at the backof the house-generally in a yard or area.Pass the cane up the pipe a foot at a timeand suddenly jerk it back, passing it up alittle further each time. You need notbe afraid of hurting the pipe. This isalways of heavy gauge lead, which is usedbecause it can be run with easy bends and,since it does not corrode, lasts indefinitely.The jerking of the cane and the hot waternow filtering down to the obstruction willbreak it up. A stoppage which cannotbe cured may possibly be due to a raggetting down the sink waste. A corkscrew



Showing two methods of clearing a blocked sink-first by means of a length ofcane, and (inset) by means of a force cup.

drain cleaner and professional help will benecessary. But let it be a lesson to use asink basket to receive plate scrapings andto fish for dish swabs before removing thestopper.

Clearing a Stopped GullyThere is still the possibility of a stopped

gully or syphon trap. This will be diag-nosed immediately by the fact that thegully will be overflowing and will not passaway the drainage from the sink. The fatwhich may accumulate in a gully has anobnoxious smell, therefore it is advisable topour half a cup of carbolic into the trapand get ready for dirty bailing. An empty

cocoa or goldensyrup tin smallenough to go intothe trap should beused. You will findit handier to con-vert the tin into aladle by screwing along wooden handleto it through holespunched in the sideof the tin. A quartor two of water willhave to be removedbefore getting tothe fat, of which itis possible two orthree pounds mayhave to be collec-ted. Flush downwith boiling sodawater ; pass thedrain cane throughthe upper, or outlethole from the gully,and your drain willbe cleared.

A " spring clean-ing " of your wastepipes and drains inthe way describedshould be an annualduty for the" Plumbing Depart-ment." Baths andbasins when stop-ped will yield to thesame treatment.

Fitted Basins forBedrooms

There is no easierway of bringing

an old house up to date than by installingfitted basins in the bedrooms. You have noneed to delay on the ground of expense,because half the cost is plumber's work,part of which you will save if you do the jobyourself.

The basin illustrated was fitted by anamateur plumber who realised that hewould be able to do all the work himselfexcept the " wipe " joints at the unions.The lengths of lead pipe required were care-fully measured, and these measurementsgiven to a plumber, who cut the pipes tostated lengths and " wiped on " for theconnections after the pipes had beeninstalled in position.

The materials used in the job illustratedwere as follows :-Earthenware basin, 25 x 18 in.,

complete with chromium -platedfittings and enamelled towel

£ s. d.

rail brackets . . . 2 15 0Tiles for back, or opalite, or plate

mirror . . . . . 0 15 025 ft. of k -in. lead service pipe for

hot and cold supply weighing6 lb. per yard . . . 0 12 6

3 ft. of 1 -in. (6 lb. per yard) leadpipe for " puff " . . . 0 1 6

12 ft. of lead waste pipe,14 lb. per yard . . . 0 14 0

Plumber's charges for wiping sixjoints . . . . 0 15 0

Cement, screw, saddles, etc. 0 5 0

£5 18 0

This means that your basin would costyou is. a week spread over a period of justover two years.

to

The lead trap which is fitted to all sinks, basin; andbaths provides a means of catching solid matter which

would otherwise pass into the waste pipe.

THE opening of the Courtauld Institutein London has provided English artgalleries and dealers with the services

of a specialised art laboratory similar tothose existing at the Louvre in Paris, inBerlin, and in America at Harvard. Expertadvice on the renovation and cleaning ofold paintings is part of the work of suchlaboratories. But to -day, when the genuineold master fetches prices which are some-times fabulous, the more interesting branchof their activities is concerned with identify.ing the genuine from the spurious, or eventhe obvious forgery.

The sign manual of an artist is thecharacter of his brush strokes. Under themicroscope the brushwork of an artistisas clearly distinguishable as a style of hand-writing. One artist might have workedwith a bold sweeping stroke, another withslight meticulous touches. Forgers awareof this sometimes make electrotype photo-graphs of portions of a genuine work, andthen use the electrotypes as stamps toimpress exact facsimiles of brushwork onthe soft wet paint of their forgery.

NEW ART LABORATORIES

Imitation and GenuineCracks are usually regarded as the hall-

mark of age. Though the forger can scratchin artificial cracks, the microscope distin-guishes clearly between the imitation andthe genuine fissures of age.

A forgery may pass all the preliminarytests of the microscope, but it cannot evadethe sheer chemistry of oils and paints. Tothe expert the oil used in binding a painttells its own age. The refraction of lightby oil increases gradually with age longafter it has set, and can be measured withsuch accuracy that by itself it often datesa painting to within a century.

PaintsPaints date themselves. Thus a rare

deposit of azurite blue discovered in 1450was worked out about 1650, and dis-appeared from artists' palettes from that

year. Prussian blue was first made bychemists about 1720, and became popularwith artists some thirty years later. Itis an easily identified chemical. Nopicture using Prussian blue amongst itscolours and purporting execution beforethe middle of the eighteenth century canbe genuine.

For such chemical and optical tests theminutest portions of the picture are removedin the hollow of a hypodermic needle andthen examined under a microscope by themethods of microchemistry.

X-rays have a certain limited,use. Theyshow up retouchings and over -paintings.By this means a famous Dutch picture of aman drinking, " The Toper," was shown tohave started life as a simple portrait of aDutch gentleman. A later artist had addedthe detail of a raised wineglass. X-raysshowed the over -painting. Externalevidence provided by an etching from theoriginal before its bibulous character wasconferred upon it showed that the X-raysbad detected the original intention of thepainter.



THE qkOOVIAAn account of an interesting tourof the Lincolnshire Co.'s SugarWorks, describing the variousprocesses through which the sugar

beet passes.

SUGAR is not only a valuable food initself, but is also the raw material of ahost of important industries, so that

its manufacture is a matter of great eco-nomic importance.

We obtained some idea of its valueduring the war, when it was exceedinglyscarce, and was consequently severelyrationed, the wholesale price rising to 1608.per cwt., that is 18. 5/d. per lb.

There is perhaps no foodstuff in generaluse the manufacture of which demands somuch technical and scientific skill andmechanical ingenuity.

Sugar is found in nature as a constituentof the sap of several varieties of tropicalpalm trees, the sugar -maple tree, the sugarcane and the sugar beet ; but for allpractical purposes we need only considerthe last two, as almost the whole of theworld's sugar supplies are made from oneor other of these.

The writer has visited cane sugar factoriesin the West Indies, and beet sugar factoriesat home, and can consequently describethe process of manufacture from either rawmaterial, which in the main is the samefor both, only differing in detail. We willcommence with a brief summary of theprocess of sugar making from the cane.The canes are harvested in the fields,removing the green leaves and loading therods, which in the West Indies are from10 to 20 ft. long, but in Madeira from6 to 10 ft.' only, owing to the cooler climate.

Sugar making from the CaneAt the factory they are passed through

a grinding mill, which crushes the cane flatand drives out the juice. The largerparticles of foreign matter are removed bystraining, and the result is an almost opaqueturbid liquor containing much fine solidmatter in suspension, and also solublesubstances which can only be separated byprecipitation. The liquid is placed in alarge tank, and quicklime is stirred in. Itis made into a lime cream before addi-tion to the juice, and then carbon -dioxide

NCE OF SUGGARBy GEORGE LONG

(CO2) is added. Sometimes sulphur di-oxide (SO2) is used instead

'it has a very

powerful bleaching effect, but modernEnglish food regulations are very severe onresidual SO2, so that its use demandscaution.

After a time the liquid separates bysettlement, leaving an almost clear juiceon top and a much thicker solution below,which requires careful filtration. Theunfiltered juice is next passed through ajuice filter press (which will be fullydescribed later) and the result is a brightsugar solution, free from all foreign matter,but still of a brownish or yellowish colour.If we separate out the dry crystals at thispoint in the process (as some factories do

Showing amodern beet

factory.

abroad) the result is a raw sugar, of a darkcolour.

The next process demands a high degreeof technical skill, as by it the brownish,dark, unappetising sugar is decolourisedand made a beautiful white, while theflavour is much improved also. The juiceis mixed with finely -powdered charcoal ina closed pressure vessel by means of elec -trically-driven paddles, and is then forcedby steam or air pressure through therefining filter. This consists of wood ormetal plates, usually about 2 to 3 ft. square,which are covered with filter cloths. Thecarbon particles are imbedded in the mesh ofthe cloths, so that the juice passes througha layer of it before the process is complete.

Showing the huge evaporating pans in which the sugar solution is evaporated.



A set of centrifugal separators in which the sugar is

crystallised out.

Concentrating the Sugar SolutionWe now have a perfectly refined sugar

in solution, and this has to be concen-trated. Here the refiner takes advantageof the old scientific principle of our schooldays, that the temperature at which aliquid boils varies with the pressure. Thesugar solution is evaporated in closedvessels, heated by steam coils, and kept ina partial vacuum by means of an air pump.By this means it is possible to concentratethe syrup at a temperature far below thatof boiling water, and this helps to producethe splendid white colour which is such afeature of British refined sugars that somecountries cannot compete with it, and sendtheir own raw sugars here to be refined.The concentrated syrup is then placed incentrifugals to separate out the crystals.A circular drum or basket of fine wire meshis placed inside a larger drum, and is filledwith the concentrated syrup. The basket isthen rotated at a speed of from 800 to1,200 revolutions per minute, so that theliquid portion is thrown out through themesh, leaving the crystals behind. Theliquid consists of syrupy non -crystallisingsolution called molasses, from which comevarious grades of treacle, and in the WestIndies rum is made from it.

The above is a bare outline of the processof sugar manufacture, which is the same forboth cane and beet sugar from the pointwhere the juice has been expressed. Sugarmade from beet or cane is identical in com-position, being derived from the naturalsugar present in the sap of each.

The Beet Sugar ProcessThis process commences with the arrival

by rail of the beetroots. They are shotfrom the trucks into bins, under which is acovered water channel. When the beetsare to be used they are dropped into thisstream, which removes dirt and conveysthem to the slicing machine. This is fittedwith from eight to twelve pairs of knivesfixed on revolving discs which spin at aspeed of from 100 to 150 revolutions aminute. The usual plan is for the slicingmachine to be in the centre of a battery ofdiffusers, which are arranged in a circlearound it and are fed in turn from theslicer by means of a long hopper. Thisprocess is a wonderful example of prac-tically automatic machinery ; as one diffuser

Unloading beet at Lincolnshire Sugar Co.'s works.

is being filled with fresh slices of beet,another is evacuating the exhausted roots,which are shot into a conveyor to be madeinto cattle food. The diffusers are uprightcylindrical vessels, three-quarters of whichis sunk below the level of the floor. Eachis lined with perforated metal, which retainsthe pulp but allows the sugar juice to passthrough. Hot water is fed through eachdiffuser in turn, until all the sugar is extrac-ted. As the sugar in each diffuser reachesfull strength, it is drawn off and pumpedinto the main tank. It is a fascinating studyto observe this clever machinery in fulloperation ; each diffuser in turn is filled withbeet, exhausted of sugar, emptied of wastebeet, and starts again, and so around thecircle throughout the day ! There are -aboutten washings to each diffuser.

When sugar was dear years ago thediffusion method was also used with canesugar, the bagasse, or crushed cane, beingwashed out with water to extract thesugar still remaining, but on my, last visitI found this method had been abandoned,as with raw sugar worth only 4s. 6d. a cwt.or id. a lb. in the Indies, it would not payto extract any more, especially as freshcanes cost only 128. 6d. a ton delivered tothe works by the unlucky grower.

The cane process, like the beet, is con-tinuous. The canes are fed into a travel-ling band or runway, which carries themthrough the crushing mills, which consistof a series of grooved rollers, so placed thatthe lines joining their centres form anequilateral triangle. The crushing millssmash the cane flat and squeeze out thejuice, and the bagasse or waste cane fires theboilers of the works-no other fuel being used.

The Filter PressesThe filter presses consist of square plates

of wood or aluminium, held in racks,through which first the juice, and after-wards the sugar solution, are forced bysteam or air pressure. In the first, or juicefiltration, special filtering earths are used ;the British product is mined in NorthIreland and is called diatomite, while itsrival kieselguhr comes from Germany.These earths look like fine sand, but underthe microscope are found to consist oflovely little sea -shells. As with the carbonin the refining process, the diatomite ismixed with the juice, and so spreads over thefilter cloths and holds back all the impurities,while the clean juice passes through.

The photographs were taken at theLincolnshire Sugar Co.'s factory.

A set of filter and refining presses.



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look -in NOW! This splendid30 -line receiver gives perfect receptionof the present televised programmes.The Kit comprises EVERY PART forassembly, including B.T.S, UniversalBall -Bearing Motor for Mains or Bat-tery operation ; controlled resistances ;laminated, ready - assembled chassis,with all component fixing holesmarked ; Stroboscopic 16 -in. scanningdisc and stand; lens and lens holder;improved type TELELUX Neon Lampand Holder ; FULL - SIZE BLUEPRINT with ASSEMBLY; WIRINGand operating instructions. If re-quired with B. T.S. SynchronisingGear, 2//6 extra.

FROM ALL DEALERSIf any difficulty, send direct. Askfor lists of B.T.S. Short Wave andTelevision Components and Kits.

Short Wave and Television SpecialistsBRITISH TELEVISION SUPPLIES, Ltd.BUSH HOUSE, Dept. Pr.M.1, LONDON, W.C.2

Telephone : Temple Bar 0134

ARE YOU INTERESTED INSCALE MODEL RAILWAYS?

If so, cur "00 " gauge models cannot fail to interestyou. We supply a full range of constructional parts,easily put together, for making models definitely toscale, at prices within everyone's reach.Our " 00 " Track, completely assembled and painted,is only 2/6 per 36 ins. (62 sleepers per yard), or,unpainted, only 2/- per 36 ins., straight or curved.Full electric control is obtained simply, and greatlyadds to the fascination of Model Railway work. Ifunable to call, send 2d. for Track sample and lists to

The "00" Specialists

HAMBLING'S26 CharinfiCrosTs RdB.,,L4o7n0d4on, W.C.2

WIRELESSTE LEYISION

Television is the comingboom in wireless-it willbring even greater pros-perity to the industry andcreate many more opportunities for acareer. Men who foresaw the broadcast-ing boom made good-be trained andprepared for this television boom whichmust follow as surely as night follows day.

At the WIRELESSCOLLEGE studentsreceive training in all thelatest developments in all

branches of the Wireless profession.Marine, Aircraft, Manufacturing, Design-ing, Experimenting, Sales and Service, etc.College on sea front. Write for freeprospectus.

STUDENTS ACCEPTED AS BOARDERS. TRAININGFEE CAN BE PAID AFTER APPOINTMENT SECURED

The WIRELESS COLLEGE COLvvAL EBSA Y

S.E. 5A." WELCOM "

CONSTRUCTIONAL KITfor building

1/48th Scale ModelINCLUDING all parts required toproduce a realistic Scale Model. Allmachine work has been done-onlysimple handwork is required for

successful assembly.

SEE EDITORIAL COMMENT ANDCOMPETITION ON PAGE 370

Price 1/- completeFrom all Stores and Dealers, or direct from the Makers

13 Post Free

Other kits available include :-ComperSwift, D.H. 60, Puss Moth, Percival Gull,Autogiro, Sopwith Camel, Bristol Fighter,Hawker Hart and the WORLD-FAMOUS

D.H. COMET.

WILLIAMS, ELLIS & CO. LTD., KELVIN HOUSE,82 FARRINGDON ST., LONDON, E.C.4

A=111=MIN

RECTIFIERSFor the operation of Model Electric Railways, etc.

MODEL MR 105. Output 6, 8 or 10 volts at5 amps. Incorporating Reversing ResistanceController, Westinghouse Metal Rectification.

£4 4 0COMPLETE LIST ON REQUEST.

Also POINT MOTORS, REVERSING RESISTANCECONTROLLERS, VARIABLE RESISTANCES, etc.

Obtainable from stockists of Model Railway apparatus or

SHENPHONE ELECTRICAL PRODUCTS226 HIGH ROAD, LEYTON, E.I0

GRAFTON ELECTRIC COMPANYBOAT MOTORS FOR THIS SUMMER !

THE"CHALLENGER

Low CurrentConsumption,PermanentMagnet Field.

4 v. approx. -4a.7/6

Large model,4v.approx..6 a.

11.6Post free.

THE " NIPPY " (illustrated on right), Two to 4 Volts -THE "HERCULES " (illustrated on left), Two to 4 Volts

Send for Illustrated 1935 Catalogue.Post free 3d.

(DEPT. P),54 GRAFTON STREET,TOTTENHAM COURT ROAD,

W.I

4/62 6



WIPTIIILESS EXPEIlr

THE illustrations accompanying thisarticle show that the receiver followsvery closely the design of a short-wave

receiver, and, in fact, the apparatus hasbeen designed to cover this wave -bandprimarily, but may be adapted for use onthe normal broadcast bands by the use ofsuitable coils. Therefore, when a set ofcoils has been obtained, the receiver willcover all waves from about 13 to 2,000metres. After some experiment it wasdecided that the best all-round effectscould be obtained without the complicationof an H.F. stage, and consequently thecircuit follows the welltried detector andtwo L.F. arrangement which has provedso popular amongst amateurs for the pastfew years.

The CircuitThe detector stage is carefully de-

signed, and unnecessary frills andtrimmings have been avoided. Thegrid leak is joined to the negative sideof the L.T. supply, although in actualuse this could be changed round tothe positive supply if it is foundthat increased sensitivity is required.Coupling between first and secondvalves is of the resistance -capacitytype and the values chosen providegood amplification with good quality.Between first L.F. and output stagesan L.F. transformer is employed, andthe ratio has been so chosen to providegood step-up without risk of instability.It will be seen that this stage is de -coupled, thus reducing the risk ofinstability, and with this transformera slight fillip is given to the lowerfrequencies. Decoupling ensures thatthe circuit will be quite stable, evenif operated from an inefficient mainsunit, and thus battery troubles maybe avoided by using this type ofsupply.

1MAITER

THE WORLD -SPANALL WAVE THREE

Full constructional and operating detailsof a three -valve receiver designed for useon short, medium and long waves.

ConstructionThe wiring diagram and illustrations will

enable the receiver to be made up almostwithout the necessity of careful explanation.For those to whom receiver construction isnew, however, the following notes will nodoubt prove of value. The chassis must bedrilled first for the valveholders and thesmall terminal strips. To clear the valvepins a 1 -in. diameter hole will suffice, butwhen screwing the holders on to the chassistake care that the top of the metal socketsdoes not come into contact with themetallised surface of the chassis. A 1 -in.drill will enable the socket strips to beneatly mounted, and finally all the compo-nents should be attached to the chassis.The actual wiring will be found simple,although some constructors prefer to mount

the components one by one, placingthe wires to each component as it isplaced in its position, and workingthrough the theoretical circuit. Oneword of warning is necessary regardingthe mounting of the small componentbrackets. That which holds the seriesaerial condenser must not come intocontact with the metallised surface,and therefore this should be cleanlyscraped away with a knife, whilst theother brackets must make good contactwith the chassis. Owing to the factthat the chassis only has the uppersurface coated, the brackets on theunder -side automatically become in-sulated as they are attached to theplain wood. Take care, therefore, touse fairly short screws for mountingt hese, in order that the screw willnot penetrate through to the metalsurface.

WiringComplete the wiring with fairly sub-

stantial wire, making good soundsoldered joints if possible in order to

Three photographs of the receiver showing the neat and compact layoutof the components.



avoid difficulties due to corrosion or loose-ness at some later date. When wiring iscompleted connect up the batteries, theH.T. positive lead being plugged in to the120 -volt socket of the H.T. battery and theH.T. - lead into the socket on the batterysimilarly marked. The G.B. positive leadshould be inserted into the positive socketat the end of the bias battery and G.B. 1

should be inserted in the (or 1.5) voltsocket, with G.B. - 2 into the 4.5 -voltsocket. To keep down the total H.T.consumption the -bias applied to the lastvalve (that is, G.B. - 2) may be increasedup to 7.5 volts, at which figure the totalanode current consumption will be foundto be approximately 6mA.Adjusting the Receiver

The aerial and earth leads should now beconnected, and the loudspeaker joined tothe appropriate terminals, and the switchset to the " On " position. Naturally acoil will be inserted into the coil holler,and this should be of the type designed tocover the waveband upon which it isdesired to listen. In order to simplifyadjustment when first working on the shortwaves the coil 6R will prove most useful,and the reaction control should be slowlyturned until a breathing sound is heard.Turning the tuning control will now enablevarious stations to be picked up, but if thereaction adjustment is carried too far theonly sound which will be heard when tuned

(Continued on page 366.)

LIST OF COMPONENTS FOR THEWORLD -SPAN ALL WAVE THREE

Two Coils, Type S.P.C. and S.P.D. withBase S.P.B., (B.T.S.).

One .00016-mfd. Tuning Condenser, 02,Scientific (Eddystone) with 933WDrive.

One Aerial Condenser, .0001 mfd., Cl(Eddystone).

One .0002 Reaction Condenser, C3(Eddystone).

Two extension spindles, 3 in., No. 943(Eddystone).

One 1-mfd. Fixed Condenser, C5 (T.M.C. ).One .0001-mfd. Tubular Condenser, CA

(T.M.C.).One 2-mfd. Fixed Condenser, C7 (T.M.C.).One .01 Tubular Condenser, C6 (T.M.C.).One 5-meg. Fixed Resistance, R1

(Amplion).One 50,000 ohms Resistance, R2



(Amplion).One Transformer (B.T.S.).One microfuse, 100 mA.One On -off Switch (Ward and Goldstone)One H.F. Choke, Type R4/406 (Ward

and Goldstone).One 500,000 ohms potentiometer, R4

(13.T.S.).Three Valveholders, 4 -pin Airsprung

(Clix).Six 2 -in. Component Brackets (B.T.S.).Two Terminal Strips, A.E. and L.S.

(Belling Lee).Five Wander Plugs, H.T. H.T.

G.B. -F, G.B. - 1, G.B. -2 (BellingLee).

Two Spades, L.T. + and L.T. - (BellingLee).

One Metaplex Chassis, 10 x 8 x 3 in.(Peto Scott).

Three Valves, D210, L210, P220 (Hivac).Batteries, 120 -volt H.T., 9 -volt G.B.

and 2 -volt accumulator.Speaker, Amplion " Dragon."

Al

MB

0002 MFG)Ac'EAcrioNCO/YDENSER

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An above and underneath chassis view of the World -span All Wave Three.



41VAcTHE SCIENTIFIC

VALVE

Hivac have brought the miniature receiverinto the sphere of practical radio by theintroduction of a

RANGE OF MIDGET VALVESThe HIVAC XSG Screen GridValve-the only one of itskind-makes possible a useful rangeof reception, thus removing the snagwhich has so completely restrictedthe uses of " pocket radio "The XD Detector Valve is suitablefor R.C.C. or transformer couplingThe XL L.F. Valve possesses a

degree of Sensitivity hitherto un-attained in Midget valves...All types have the low consump-tion of .06 amps. at 2 volts.Full details and characteristics of these Hivac Midget Valves

are given in Folder "M.P.M."

15/6

10/6

10/6

HIVAC SPECIFIED FOR THEWORLD -SPAN SHORT-WAVE 3D21 0..3/9 L2 10..3/9 P220..5/6Send for Hivac Valve Guide "P.M.", it gives full details of the

Hivac range of battery and mains valves.

HIGH VACUUM VALVE CO. LTD.,1 13-1 17, Farringdon Rd., London, E.C.1

CLIX "AIRSPRUNG"Chassis Mounting Valveholders

These Antimicrophonic Valveholders-Damp out actual physical shocks to the

valve.-Insulate the valve from consistent

vibration set up by the transformeron the chassis.

-Counteract and absorb the air pulsa-tions set up by the increasedacoustic output of modern receivers.

ANTIMICROPHONICThe CLIX patented resi-lient sockets embrace thevalve pins, both movingtogether as integral partsin contrast to the chafingmovement resulting frombadly designed pressed

SPRUNG PlArE sockets or springs whichcause microphonics.

" AIRSPRUNG "4 -pin, 1/2 ; 5 -pin, 1/3 ; 7 -pin, 1/4.

Specified for the"WORLD -SPAN

SHORT-WAVE THREE"

IDEAL for S/W WORKWith the absence of metalsprings and the minimumamount of material em-ployed, the sockets arepractically air insulated,thus embodying theessentials of a super short-wave valveholder thatcannot be surpassed.

Illustrated Folder "P.M." and Leaflets free on request.

LECTRO LINX LTD.

COMPONENTSWhen anyone mentions the name " Amplion "you invariably associate it with Loudspeakers,because for years " Amplion " Loudspeakershave been held in high esteem by all set de-signers and home constructors. Now the name" Amplion " has a much wider meaning ; itembraces not only Loudspeakers but Re-

ceivers, Radiograms, Pick-ups, Cartridge Fuses,

Fixed Condensers, Wire -wound Resistances, etc.

Amplion Components carry theAmplion reputation for quality andefficiency. They are often listedamong those " specified " by well-known set designers.

MR. F. J. CAMMHAS CHOSEN AMPLION

RESISTORSAND ALSO AN AMPLION

"DRAGON"LOUDSPEAKER

for his"WORLD -SPAN

SHORT-WAVE THREE "

Amplion Resistors from 50 to100,000 ohms are of the wire -woundtype ; this method of constructiongives the most reliable and consistentform of resistance. All values I/ -each.

AMPLION FIXED CONDENSERSThese Condensers are guaranteed to havepassed rigorous tests, and the most widelyused and specified ones are the Type TB.700 volts D.C. Test. 350 volts D.C. working.Other types have D.C. Tests of 1,650, 2,000 and2,500 volts.TYPE TB.I mfd. 1/10 .25 mfd. 1/10 -5 mfd. 2 -

I mfd. 2/6 2 mfd. 3/6 4 mfd. 5,6

AMPLION CARTRIDGE FUSESIt costs only 6d. to give full protection to thevalves and valuable components in yourreceiver. Fit an Amplion Fuse. Any ratingfrom 60 m,a. to 3 amp. for battery or mainssets. Cost only 6d. each.

AMPLION LITERATUREThere is a special leaflet for every Amplionproduct. Interesting and useful informationthat is yours for a Postcard request.

AMPLION (1932) LTD.82-84 Rosoman St.,' Rosebery Avenue, London, E.C.1

79a ROCHESTER ROW, LONDON, S.W. 1 Telephone : Clerkenwell 5440-5441



(Continued fromPage 366.) Qs

C7

GB. -2

Afro

LT -

FUSE

The circuit diagram of the World -span All Wave Three.

to a station will be a loud whistle. There-fore, as soon as such a sound is heard,slacken off the reaction control and slightlyreadjust the tuning control. If the reactionis turned back too far the station may belost, and thus it becomes rather necessaryto carry out these two adjustments verycarefully. Continuous wave Morse signalswill be heard when the receiver is oscillating,but speech and music will only be resolvedclearly when just off the oscillation point.If it is found that in certain positions thereaction control has no effect, the seriesaerial condenser should be adjusted, andthus it becomes necessary to find a positionwith this condenser where reaction can beobtained throughout the tuning range.Volume Control

When using headphones it may becomenecessary to reduce the volume slightly,and for this purpose a volume control isfitted to the receiver. On most short-wavestations this control will not be used andshould be set to its maximum position, buton the broadcast band it may be found veryvaluable in enabling searching to be carriedout by means of the headphones.

This control is of the type which providesa very smooth variation in volume and does

5

ea+

not introduce distortion. Therefore, whenthe receiver is used close to a powerfulbroadcast station, and it is found thatsignals are too loud, it may be used forreducing the volume without introducingany ill effects.Aerial and Earth

When using the receiver for the shortwaves the design and efficiency of the aerialand earth system should receive carefulattention. The customary 100 -ft. aerialwill not be productive of the best results,and, in general, a short vertical type ofaerial will be found to offer much betterresults. If, therefore, you have at presenterected one of the large types of aerial,simply disconnect the lead-in, and use thisas the aerial, when, no doubt, you will findthat it is capable of bringing in all thestations you require. Care should be paidto the insulation and the wire should bekdpt at least 18 in. from the wall or otherearthed bodies. The earth itself shouldpreferably be of the buried metal type, witha good stout wire joined to it, and somesystem of keeping the earth moist should beadopted. If this type of earth cannot beused, a good sound connection to a mainwater pipe may be used.

/0"

5 /4tu

The layout showing the position of the knobs.

sPEKE Aerodrome, Liverpool, is to befitted with the latest type of wirelessapproach beacon to assist aeroplane

pilots entering the airport in bad weather.The installation of the beacon equipmentwill be carried out by the Marconi Company,to the order of the Liverpool Corporation.

The main approach beacon is of the auraltype, and will operate on a medium wave-length, so that any aircraft fitted with anormal type of aircraft -receiving apparatuswill be able to use its service. In additionto the main beacon, there will be two" marker " beacons which will indicate tothe pilot when flying along the correct lineof approach, first, when he is at a distanceof three miles from the aerodrome, and,second, when he passes over the boundaryof the aerodrome.

How the System worksThe approach beacon constitutes a

method of indicating by wireless the bestroute into the aerodrome, providing a sortof invisible causeway that can be followedby the pilot even when the signs and land -

A NEW WIRELESSAPPROACH BEACON

marks that he normally uses are invisiblethrough. fog, heavy rain or low cloud.

This is done by arranging the transmitterto send out a series of distinctive signalsdirected alternately to each side of thecourse. At Speke the beacon will transmit aseries of Morse dots to one side, and a seriesof dashes to the other. The transmitterwill be timed so that the dots on the oneside occur exactly during the silence periodsbetween the dashes on the other side. Inthis way an aeroplane flying on the correctcourse will receive the dot and the dash atequal strength, and, owing to the timedalternate transmission it will sound as onecontinuous signal.

If the aeroplane were to deviate to rightor to left froin this course, either the dots orthe dashes would be received at greaterstrength. This provides an indication to

the pilot that he is off course, and also towhich side he has deviated.

The approach beacon at Speke is notintended to have a long range, as direction -finding facilities of this kind are available,but it is specifically for the purpose ofbringing aircraft straight into the airporton the best course. The purpose of the firstmarker beacon at three miles from theaerodrome on this course is to warn thepilot that it is time to begin losing height,while the second informs him that he haspassed the boundary of the aerodrome andis actually over the landing field. Thesemarker beacons will be audible to the pilotwithout re -tuning his receiver as he passesover them, and each marker will have its owndistinctive and easily recognisable signal.

The EquipmentThe main beacon transmitter at Speke

will be a compact apparatus contained in ametal -screened cabinet and operated directfrom the local electric supply. Its aerialsystem will be low and unobtrusive, notexceeding a height of 20 ft.


May, 1935 NEWN ES PRACTICAL. MECHANICS 369

A composite picture indicating the influence of aircraft on other forms of travel. Little was known about streamlining until aircraft engineers investigated airflow bymeans of wind -tunnel tests.

Designs for Petrol -driven ModelsSINCE the publication of my handbook,

" Power -Driven Model Aircraft," I havebeen inundated with requests for work-

ing drawings of a model into which eitherthe Atom Minor, the Hallam, the Grayspec,or the Brown Junior motors could beinstalled. Readers will have gathered fromprevious issues that I have made thesevarious engines, and that they all work

being easy to start anddeveloping sufficient power to fly a modelweighing up to 5 lb. Several designs formodels are given in the book to which Ihave referred, and I am now at work on adesign which will be published in thesepages. I have decided that all points ofview would best be served by making thisof the Pusher type, with the engine andpropeller arranged between the mainplaneand tail. Most of the experiments con-ducted by others in this interesting fieldindicate that in the early stages the modelfrequently crashes, necessitating severalrepairs and long delays before the model isa satisfactory flier.

It is a fact that for some reason or otherCanard or Pusher models are more satis-factory in every way than tractor machines.Such may look more orthodox, but they donot remain intact very long. A modelwhich is a satisfactory flier and continues tobe so without frequent breakages has muchto recommend it ; a model which does notrequire tricky adjustment has more torecommend it ; one, which, when it doescrash, does not wreck its engine, has evenmore to recommend it.

These desirable features are found toexist in the type of model to which I havereferred, and I would urge my readers notto risk wrecking their miniature petrolengines (they are fairly expensive to replace)by endeavouring to ape full-size machines.Such a model will not remain intact longenough for you to admire its appearance.

Loading ,.

I have decided that the wing span shouldnot exceed 6 ft., and by employing anaspect ratio of 6 to 1 this gives the chord as12 in. Employing a loading of, say, 6 oz.to the square foot, this brings the totalweight of the model to 3 lb. Now I havefound that this weight can easily be adhexedto. If you employ a heavier loading, the

MODELAERO

TOPICSBy F. J. CAMM

speed of take off and the landing speed willbe fairly high. With a loading of 6 oz. tothe square foot and using a moderate wingsection, the speed can be kept to less than20 miles an hour. I am aware that somepetrol -driven models have weighed as muchas 6 lb., but I am certain that this weightinvolves many structural problems. Thehigher landing speed when heavierloadings are used means a strongerchassis, which means a stronger fuse-lage, and so you find the problemtravelling in a vicious circle. A totalweight of 3 lb is a convenient figureto work to. It does not call fo;specially light construction, andenables a reasonable amount ofmetal fittings and substantialattachments. I do not proposeto make use of thread binding, orBalsa wood ; I prefer to usesilver spruce and birch, duralumin tube,metal straps, and sockets, in order to pro-vide a rigid and workmanlike job. I sawone model last year with the engine pre-cariously mounted in a tractor model on abent piece of /-in. x iron by means oftwo bolts. Apart from the fact that thepiece of iron was heavy, it caused the thrustline to alter every time the model landed.Endeavours to correct this caused the frontof the fuselage to break off.

The ChassisI find that the chassis is usually the

weakest part of such designs. I do notthink there is any need to adopt full-sizepractice in the chassis. Provided that low

pressure air tyres are used, there is no needto adopt any other form of shock absorber.Such tyres will take the load of landingwithout wrecking the chassis. Chassiswhich are flexible can be mixed blessings inthat they enable the wing tips to come intocontact with the ground and cause damagewhich would otherwise not occur. Severalsuitable wheels are now on the market, andI hope also to give instructions for making apair from rubber balls. For the chassismembers I propose to use duralumin andsteel tube, and to make it of the dividedaxle type. Instead of a rear skid I intendalso to use a rear wheel of small diameter toshorten the take -off.

WingsI propose to make the wings in two

sections, each of the mono -spar type, whichwill push on to stubs extending fromthe fuselage, and so attached thatimpact will detach them. I do not

like the rubberring method

of attachingwings; this looksunsightly, andhardly in keeping

with the arguments sooften advanced againstfreak models.

The position of the wingwill be fixed, any slightadjustment necessary to

the position of the centre ofgravity being effected bymovement of the coil and

The Brown Junior petrol engine, marketedin this country Stuart -Turner Ltd.


I.


The correct method of launching a model pterodactyl monoplane. The sketch showsthe positive angle of incidence at the centre section, and the negative wing tip.

battery. Thus, once the porrect position ofthe C.G. has been found the model willremain in flying trim. The rubber bandmethod is unsatisfactory from many otherpoints of view. I have seen models crash toearth due to the wing lifting off the fuselagewhen a gust of wind has struck the undersur-face of it. The stub method of attachmentensures that the wing remains rigidly fixed.An adjustable tail elevator will, of course,be provided.

ControlsThe engine controls will be brought out

to small levers and will consist of advanceand retard lever, air control, jet control,ignition switch, and a two -pin plug andsocket, so that the engine can be run upfrom an accumulator switched over to thedry cell in the fuselage. I have found thatthe Brown Junior once warm will start off1 volts, and from cold on a 4 -volt dry cell.For those readers who elect to use an enginewhich requires a higher voltage or anaccumulator, the two -pin plug will, ofcourse, come in useful. Ignition is, ofcourse, by means of a fixed coil. Myexperiments with trembler coils havereminded me of my first motor cycle, whichused this form of ignition. There is

.incessant trouble with the contacts and thetrembler blade, and for model aircraftpurposes I do not recommend it.

The AirscrewI have tried both wood and electron

airscrews, and find that the latter, althoughslightly heavier, are better, since theyprovide just that extra bit of momentumwhich makes starting easy. The airscrewdiameter is 13 in., and the pitch 9 in. Theefficiency is thus not too high, but adequatefor the load. These small engines do notrun really satisfactory at low speeds, and itis not easy to make a model airscrew whichis efficient or rather highly efficient at3,000 revolutions per minute. The diameterand pitch to which I have referred andwhich, of course, are largely decided by theflying speed and the loading seem to providea happy compromise between the opposingtechnical factors. Airscrews in electronare available from a number of sources, sothat the reader will be saved the trouble ofsending a wooden pattern to the foundry.My experiments with geared airscrews donot lead me to recommend this form ofdrive.

The FuselageAs can be gathered from the foregoing

remarks, the fuselage will be short, justsufficiently tong, as a matter of fact, toaccommodate the engine, tank, coil, andbattery and chassis. The tail will becarried on booms, so that the model caneasily be dismantled and packed into areasonably small space. Portability, Irealise, is an important point, not only so

SPECIAL COMPETITION

For the best model of an S.E.SA aeroplanemade from a set of " Welcom " aeroplaneparts (see paragraph on this page) we willaward the following prizes :-

First Prize : £1 10 0.Second Prize : £1 0 0.Third Prize : 10s.

Fifty Consolation Prizes of books.

The following rules must be compliedwith :-Rule 1. Every model must have the name and

full address of the competitor written inink on the underside of the fuselage.

Rule 2. Models must be made from " Wel-corn " parts.

Rule 3. Latest date for receipt of entries isMay 26th, 1935.

Rule 4. Stamps for the return of the modelmust be enclosed.

Rule 5. The Judge's decision is final and anexpressed condition of entry. TheJudges will be the Editor of " PracticalMechanics " and Mr. Williams, ofWilliams, Ellis & Company, makers of" Welcom " parts for the S.E.SA.

Rule 6. Models must be sent securely packedand in a box suitable for their return, andaddressed to The Editor, " PracticalMechanics," 8-11 Southampton Street,Strand, W.C.2.

that it may easily betransported, but also sothat it may be stored.

Full-size Blue PrintsIt is not possible to

give a series of full-size ribsections in this journal,so it is proposed to issuefull-size blue prints of thecomplete model for anominal sum. Thesediagrams will, of course,be reproduced in thesepages, but it is thoughtthat readers who intendto build the model wouldprefer to work from afull-size diagram. Theseblue prints may be usedfor marking off thematerial whilst the ribsections can be pastedon to the millimeter three-ply and fretted or cut withscissors to correct shape.

Miniature PlugsThe Brown Junior miniature petrol

engine makes use of a plug which is pro-portional to the size of the engine, and it isabout half the size of the miniature plugnormally supplied. I suggest that allmakers of model petrol engines shouldmodify their designs to suit." Wekom " Constructional Sets

Many readers are interested in miniaturescale models of famous aeroplanes. Ishould like to draw their attention, there-fore, to the " Welcom " Constructional Setssupplied by Williams, Ellis & Co. Ltd.,Kelvin House, 82 Farringdon Street, E.C.4.These realistic models may be assembledfrom the parts which are supplied completewith all the necessary materials fof the lowprice of is. per set. The models aredesigned to a uniform scale of 1/48th full-size, and sets are available for the ComperSwift, the D.H.60, the Puss Moth, thePercival Gull, the Auto Giro, the SopwithCamel, the S.E. 5A, the Bristol Fighter, thefamous Hawker Hart, and the D.H. Comet.The materials are partially finished, butneed a minimum of attention in order tobring them to the finished form. Allmachine work has been done. The partlyfinished unit leaves just sufficient handworkto maintain the interest and to provideroom for individual touches.

The reader's attention is drawn to thecentre column of this page in which appeardetails of a competition for the best modelof the S.E.5A made from " Welcom "Constructional Kits.

If any readers have completed the modelsdescribed in my handbook on Power DrivenModel Aircraft, I shall be glad if theywould send me a photograph and a briefdescription for publication, and to pay forall such photographs which are published.I know that several of the petrol enginesdescribed in my book have been built andare successfully running, and for the

A:

a.e.

THETWO STANDARD WORKS-

MODEL AEROPLANESAND AIRSHIPS

POWER DRIVEN MODELAIRCRAFT

Each containing 96 pages and over 120 illustrations

1/- each or 1/2 by post from Geo. NewnesLtd., 8-11 Southampton St., Strand, W.C.2.

FLAT

ARCHED

AMBERED

STREA111-111C

Showing various wing sections.

guidance of other readers I should like to -publish photographs of models with theengines installed. At the same time, Ishould be interested to receive photographsof what I may term free-lance models madeand designed by readers themselves. I am,of course, referring to power driven modelsoperated by compressed air, steam or petrol,If desired, such photographs will be returnedprovided that a stamped addressed envelopeis enclosed.



AN A.B.C. OFPHOTOGRAPHY

THE FIRST ARTICLE OF A SERIES

Abrasion MarksBLACK lines or markings on a

printing paper caused by friction orpressure. Only occur on certain

types of paper.

AcceleratorA chemical included- in a developer in

order to hasten the process of development.The commonest accelerator is carbonate ofsoda.

An minions release.

AchromaticThe term applied to a lens which has the

chemical and visual foci coinciding.

Acid Sulphite of Soda-See Sodium Bisul-phite.

ActinometerA device which measures or gauges the

strength of light, or, in other words, adevice for measuring actinic strength. Itgenerally consists of a piece of sensitisedpaper, and is exposed to the light until itassumes the tint of the surround. Thetime taken for this to occur is known as theactinometer time, and any exposure or stopis ascertained from a table supplied with thedevice. Another term for exposure meter(which see).

AnhydrousThe term applied to chemicals which

have had all moisture driven off. Whencompounding a formula the ordinary typeof chemical is referred to unless otherwisestated. If an anhydrous chemical isemployed the amount used will be differentfrom that given in the formula, and thevariation will depend upon the particularchemical. For instance, in the case ofsodium sulphite one-half of the specifiedamount should be used in the case ofanhydrous, but with sodium carbonate theamount required is ascertained by multi-plying the quantity given in the formula byfive and dividing by fourteen.

AlumFine white crystalline substance. Unless

otherwise stated in formula, potash alum isreferred to. It must be chemically pure.

Dissolves best in hotwater. Chrome alum ispurple in colour. Bothtypes are used for hard-ening, the latter crystalexercising a slightly morehardening effect thanpotash alum. Keepsindefinitely in a dryplace.

AmidolAbbreviated form of diamidophenol.

Fine grey powder dissolving readily in coldwater. Keeping property of the chemicalgood, provided it is kept in well -stopperedbottle. As a solution will not keep manydays. When fresh the solution is practicallyclear, but gradually darkens. Should notbe used when darker than vinegar colour.

AmmoniaClear, colourless liquid. Must be kept

well -stoppered. Keeps indefinitely in awell -stoppered bottle.

Ammonium BromideCoarse white powder, dissolving in cold

water. Keeps well in powder or liquidform. Keep bottle well corked.

Chromatic aberration is shown by coloured fringesround the candle flame.

Ammonium CarbonateLumpy, waxish crystals. Should not be

covered with powder, but may be used ifpowder is first rinsed off. Does not keepwell in either powder or liquid form..

Ammonium SulphocyanideCrystalline substance which rapidly

absorbs moisture and must therefore bekept well corked. Keeps indefinitely insolution.

AnastigmatThe term applied to a lens which has

been corrected to enable vertical and hori-zontal lines to be brought to the same focus.

Actinous ReleaseA device for operating the shutter

through the medium of a length of wirecable. It is passed through a small dia-

A well-known exposure meter of the actinometer type.

meter tube, and pressure on a plunger atone end operates a finger at the other andso operates the shutter.

AstigmatismThe defect in a lens which gives different

focal points for vertical and horizontallines. A form of curvature resulting fromthe use of an astigmatic lens.

Backed PlateOne which is coated on the back with an

opaque substance to prevent reflection andhalation. The material usually dissolvesaway when the plate is developed.

BellowsA pleated leather cone forming the con-

nection between lens and plate or film.The lens mount is fixed to the front of thebellows and the camera is thus able to closeinto a small compass.

Bicarbonate of Soda-See Sodium Bicar-bonate.

Blue Vitriol-See Copper Sulphate.

Box CameraA camera in the form of a box, that is,

with the whole structure rigid, and the lensand plate or/film-holder fixed in relation toone another. Usually no focusing is pos-sible with this type of camera, and it istherefore one of the cheapest types ofcamera.

A good example of a box -type of camera. No focus-ing adjustments are possible with this type of camera.



PROTECTIVE APRONFILM UNDER PAPER

FILM ON SPOOL

1

The daylight loader for developing films. As may be seen, the film is woundoff from the spool into a special light -proof apron, which is then removed andplaced in a cylindrical metal can into which developing and fixing chemicals

Daylight Tank

are placed. The whole operation may be carried out in daylight. to enable developmentBromide of Ammonium. See Ammonium to be carried out in daylight. The plate

tank has to be loaded in a dark room,but the process of pouring in the developer,

Bromide of Potash. See Potassium Bro- etc., may be carried out in daylight owingmide. to a special light -trapped opening. A roll -

film tank is provided with a long apron andCarbonate of Ammonia-See Ammonium a special box in which the film and the

Carbonate. apron are interwound. The apron may

Carbonate of Potash-See Potas- N EGATI V Esium Carbonate.

operations a luminousclock should be installed,capable of showingseconds clearly.

Bromide.

Carbonate of Soda-See Sodium Car-bonate.

Caustic Potash-See Potassium Hydrate.

Chromatic AberrationDistortion caused by

the uneven refraction ofan object due to differ-ences in colour.

Chrome Alum-See Alum.

LENS

Citric AcidPowder or crystalline substance.

Keeps indefinitely without any precau-tions.

Convertible LensOne in which the various compo-

nents may be used separately or indifferent focal lengths.

Copper SulphateBlue crystals which keep indefinitely, but

in solution turn cloudy with time. Maybe dissolved in hot water to speed thepreparation of solution.

Covering PowerThe extent to which a lens is capable of

giving a sharp or well-defined image.

Curvature of FieldThe term applied to a lens where the

centre is sharply defined but the edges areout of focus.

Dark RoomThe term applied to the room in which

developing, camera loading, etc., is carriedout. Any room may be converted to a darkroom by simply pulling down the blinds andin any other way cutting out all extraneouslight, but the term is strictly applied to aroom correctly fitted out for the purposeof photographic operation. Thus a speciallamp is fitted capable of shedding either ared or an orange light, and various dishesand sinks are provided in the interests ofchemical cleanliness. For certain factorial

Daylight PaperA. printing paper

coated with a slowemulsion requiringlengthy exposure to day-light in order to producean image. The imagebecomes visible as ex-posure proceeds, andonly fixing is required.An acid bath should notbe used. The normalcolour is a warm brown.

A simplebox -type daylight or

&Rom 0, artificial light enlarger. Thenegative is held at the top

and exposure controlled by the small shutter. Onlyone size of enlargement is obtainable.

then be removed and inserted in the deve-loping tank, no dark room being necessaryat any part of the proceedings. The tankfor film packs operates in the same manner

This developing dishis made of composi-tion and may beused for any chemicals. Itis light and unbreakable.

as the plate tank, a dark room being neces-sary for the preliminary loading process.

DefinitionThe clearness or sharpness of an image.

Depth of FocusThe distance over which an image will

photograph sharply. In a very large aper-ture (that is, one which has the stop almostof the same diameter as the actual lens) thedepth of focus will extend only for a fewfeet. Thus, if the camera is focused to10 ft. it will be found that objects from,say, 8 ft. to 12 ft. will be sharply defined,whilst everything nearer or farther awaythan these limits will appear " fuzzy " orout of focus. When the lens is stoppeddown (that is, smaller stop used) the depthof focus will increase, even though thefocusing point is not altered. It followsfrom this, therefore, that when taking aphotograph of an extensive view, whereboth near and distant objects are requiredto be sharp, a small stop should, be em-ployed. On the other hand, when taking aportrait of a person in the open air, a largestop should be used in order that the back-ground may be out of focus and thus enablethe attention to be concentrated on the

portrait.

DesensitiserA preparation 'containing pynakryp-

tol, which has the property of stainingthe negative in such a way that theoperations of developing and fixing maybe carried out in ordinary light. Thepreliminary staining is, of course, car-ried out in the dark room.

Desiccated-The same as Anhydrous(which see).

DeveloperA chemical agent for acting upon

the silver salts which form the principalpart of the sensitive emulsion. Whenthis salt receives direct rays of light acertain action takes place, and when adeveloping chemical comes into contactwith it a deposit is left upon the emul-sion. The process of fixing is thencarried out, whereupon the deposit soleft is madepermanent,whilst all saltswhich received

no light are removed.The deposit isopaque, and accord-ing to the degree oflight which struckit the thickness ofthe.deposit will varyon the finished nega-tive, thus producingthe lights and shadesof the original object.

(To be continued.)

A daylight tank for thedevelopment of a roll film in the strip.



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The Hydra, which is a monster in miniature. Althoughbarely an inch in length, it is provided with tentacleswith which it entraps unwary living creatures thatcome within its reach. The Hydra usually secures itselfto a leaf or plant stem below the surface of the water.

MAN'S allotted span of life is tradi-tionally seventy years. Many suc-ceed in living considerably beyond

this limit. A few stretch out their livesto 100 years or more. On the other hand,a large number of individuals fail to attainanything like their seventieth birthday.Despite, therefore, the present increase inthe expectation of life, an increase which is,for the most part, a direct result of theapplication of scientific discoveries to the artof living, the average stretch of human lifestill remains fairly constant at seventy years.

The phenomenon of death, on thematerial side at any rate, occurs as a result

LIVING FORDespite the application of scientific discoveries to the art of70 years. In this article is discussed methods of prolonging

of the disorganisation of the bodily tissuesthrough general wear and tear, throughorganic disease or in consequence ofaccidental destruction. The heart, forinstance, can fail owing to senility orgradual wearing out, or owing to acutedisease. Again, a bullet passing throughthe heart would permanently disorganiseits functioning. In such an instance,' theheart would have been subjected to " acci-dental " destruction.

Despite various statements to the con-trary, there seems to be little doubt of thefact that the bodies of human beings or,indeed, of any other living creatures, werenot designed for perpetual functioning.Sooner or later the animal body, due to theabove -mentioned factors, becomes unableto carry on its functions. Death, therefore,results, and subsequently, unless elaborateand usually not very satisfactory counter-acting measures are taken, the bodygradually loses its features and form andsubsides away in that long sequence ofcomplex chemical, physical and bacterialchanges to which the name " corruption "is given. Life, therefore, as we know itwith our material senses cannot go on forever. Perhaps some day the average life -span may be pushed up to 100 years oreven a decade or two beyond that limit.Such prolongation of life, however, wouldbe due to our better knowledge and morecareful treatment of the human organismand not to any radical change in the life -balance of the body.

Prolonging LifeConsiderations such as the above, upon

which most individuals will be agreed,however, do not preclude the dim possi-bility of life being lived in snatches. Sup-pose, for instance, that a man were able tospread out his seventy years of life through -

The petals of flowers frozen in liquid air become so brittle that they can be powdered upwith a hammer like thin pieces of glass.

out the centuries, living ten years in onecentury, six years in the next, a couple ofyears in the third century, and so on, his" life " could be prolonged for a very greatlength of time. An individual capable ofliving his life in jerks, as it were, would beable to gather glimpses of contemporarycivilisation down the centuries. True it isthat he would not have to form any deepsocial or individual attachments owing tothe comparative shortness of his" snatches " of life. Nevertheless, ourimaginary individual would prove a mostvaluable member of the community froman historical point of view. A man in ourown days, for instance, who rememberedclearly the ancient civilisation of Greece,who had been present on the battlefieldof Hastings and who, five centuries later,had conversed with Shakespeare in his

The water flea.

Stratford -on -Avon home, would be in aposition to throw much light upon manydoubtful historical matters. Sound re-cording and photography can now do muchin the way of handing down records toposterity, but an individual eye -witnessaccompanying such records would renderthe evidence of history complete.

The notion of living one's life in snatchesis not so fantastic as that of living con-tinually for an indefinite period. Thelatter dream of humanity has no scientificevidence on which to base itself. The " inter-rupted " method of living, however, pos-sesses at least a number of practical obser-vations upon which its technique mightpossibly be reared. Suspended animationis, of course, a well-known phenomenon.It can be entered into voluntarily bycertain individuals, notably Indian fakirsand Hindu yogis, and, in many instances,it forms the accompaniment of mysticalreligious experience. Such suspended ani-mation, however, is but relatively brief.A few hours, days or, at the most, weeksis the time limit of this cessation of bodilyfunctions, and the suspension of activity isoriginated mentally rather than physically.The " interrupted " life, therefore, cannot bebased upon such experiences.

The Effect of HeatOur bodies, being composed of matter in

its various combinations, consist, like all



20,0,000 YEARSliving, the average span of human life remains at roughlythe span of life to the amazing figure given in the title

other material objects, of vast assemblagesof particles called atoms, all of which are ina state of rapid motion and vibration. Itis the motion of these constituent particleswhich constitutes the root cause anddirecting force of the various changeswhich are continually undergone in thebodily tissues. These motions are all verycomplex in nature, and we do not under-stand them properly. There is one thing,however, which we do know about them,and that is the fact that they are influenceddirectly by heat. Adding heat to a body ora system increases the motions of its par-ticles. If you throw a man into a furnace,heat will be added to his body. The motionsof his particles will be given such anenormous increase of energy that they willfail to keep within their prescribed bounds.The bodily particles, of such an individual

Ceratia. Other minute aquatic organisms which havebeen frozen and afterwards returned to life.

will rush here and there in mad confusion,forming new chemical compounds and com-pletely disorganising and disrupting thebody. The man will burn and he will nolonger live.

When a body or system is cooled down,the motions of its constituent particles areprogressively retarded until the tempera-ture of absolute zero (- 273° C.) is reached,at which temperature the particles aremotionless. It is impossible to attain oreven to imagine a temperature lower thanabsolute zero, because at this temperaturea body contains no heat at all. If, now, aman in good health could be cooled downto absolute zero or to a temperature verynear that point, the minute particles of hisbody would have their motions arrested.The body, therefore, would no longer beable to function. The man would no longerlive in the active sense of the term. Onthe other hand, the body could not dis-organise or decay, because even such retro-grade processes require a ceaseless activityof its constituent particles. In such cir-cumstances, therefore, the body would be" held." It would remain indefinitely un-dead, un-alive. Careful thawing of the bodywould, owing to the addition of heat,restore the motions to the particles andthus, under favourable circumstances, thebody would again return to life.

Why it is ImpossibleOne big snag stands out prominently in

the above scheme. Under any known con-ditions it would be impossible to cooldown a man's body quickly enough for themotions of its particles to be arrestedinstantly. If the cooling process tookplace slowly, even if it occupied merely afew seconds of time, the different rates offreezing would destroy the balancesbetween the various organs and tissues inthe body and death, instead of frozenanimation, would result. The entire possi-bility of the scheme is dependent upon themotions of the body's constituent particlesbeing instantly " held," and this could onlybe effected by instantaneous cooling downto absolute zero, a process which, at thepresent time, is totally impossible.

Within recent years experiments uponthe prolongation of life by freezing havebeen carried on in many laboratories. Foryears it has been known that fish may befrozen hard in ice, so hard that they maybe. snapped in two with the fingers, yet,after slow thawing, they return to life andare apparently none the worse for theirexperiences. In the Polar regions thisfreezing process must be fairly common,and the marine inhabitants of thoselocalities must survive frequent periodicalrefrigeration.

Liquid air is well known in laboratoriesas an extremely powerful refrigerant.Flowers dipped in liquid air, which has atemperature of about 190° below thefreezing point of water, immediatelybecome as rigid and as brittle as glass.This temperature, however, low as it is,is a high one compared with the tempera-ture of liquid helium. Liquid helium hasa temperature of - 268° C.-268 degreesbelow the temperature of ice, and only5 degrees above absolute zero. Into liquid

The cyclops. A minute water animal which is some-times found in drinking water. This is the female ofthe species, and she carries two egg -cases full of eggs on

each side of her.

helium various small and soft -bodiedaquatic creatures have been placed andallowed to remain therein for periodsranging from a few minutes to several days.In all such instances, immediate freezingof the living tissues has taken place, themotions of the particles of the animalorganisms have been instantaneouslyarrested. A condition of life -suspensionhas, therefore, ensued. After the elapse ofthese varying times, the creatures havebeen removed from the bath of liquidhelium and very slowly thawed. In nearlyevery instance, life has returned afternormal temperatures have been reached,thus proving that it is possible to cooldown a living creature to such a degree

(Continued on page 388)

Our artist's impress'on of the " subject " about to be frozen. Around can be seen vacuum bottlesand large steel control gauges with taps. In the far background are " containers- having within

them at constant absolute zero, the bodies of other individuals in a state of refrigeration.



An electrical aura. The field of influence surround-ing a wire carrying -a current disclosed by means of

iron filings.

NO scientific subject has proved ofgreater fascination to many mindsthan that of the human aura. Around

every living body there exists from themoment of birth, nay, from a time evenbefore birth, to the instant of death apeculiar haze or " aura," as it has now cometo be termed, which, under certain condi-tions, can be made visible. This humanhaze A a product of the living body. It

sickness, varying in intensity and inphysical form according to the varyingconditions and state of the body. Soinseparably connected is this ethereal andtenuous haze with the living body that itis often referred to as the ' human atmo-sphere."

There are not many people who haveseen the human atmosphere. There are, infact, individuals to whom, apparently, thehuman haze can never be revealed, onaccount of the insensitivity of their eyes tothe rays which proceed from it. Despitethis fact, however, it would seem that atleast 60 per cent. of the persons whoendeavour to see the human aura aresuccessful in doing so ; not, perhaps, on theirfirst attempts, but, more commonly, afterthree or four painstaking endeavours towitness the phenomenon.

A few people claim to be able to perceivethe aura surrounding the human body withthe naked eye alone. Many people giftedwith second sight seem to possess thisfaculty. Clairvoyants and individualspossessing spiritualistic tendencies andpowers claim to be able to distinguish thehuman aura either at will or after they havevoluntarily attained certain trance -statesof the mind. It is not at all certain, how-ever, whether the " aura " which suchindividuals claim to be able to see isidentical with the aura of the scientificinvestigator. The aura of the scientist isdefinitely a material phenomenon. It canbe witnessed, measured and even minutelyexamined at will by the scientific investi-gator working under the right conditions.No hypnotic or trance -like conditions onthe part of the investigator enter into thequestion. The human aura is a perfectlymaterial and natural phenomenon. It is asnatural an accompaniment of the humanorganism as is the breath. Owing to itsnature, however, it is an evasive entity

FACTS eABOUT @AURAAn interesting article dealing with the " Human Haze " surrounding

the living body, and how it may be seen.

and, usually, it is only seen under veryrigidly defined physical conditions.

A Thin Luminous HazeScience in general has, as yet, given

surprisingly little attention to the matterof the human aura. Some years ago amedical man-W. J. Kilner by name-who was living in retirement at Southamp-ton, wrote a volume on the subject of theaura. In his book Kilner embodied theresults of many years of patient investiga-

The human aura, as we have alreadyexplained, consists of a thin luminous hatewhich surrounds the body. It is completelyhidden by clothing. Hence, for the purposeof experiments, the " subject " must divesthimself of his clothing if his aura is to beseen in its entirety. Usually, however, forthe purpose of preliminary experiments, asubject who has stripped to the waist oreven to the chest will suffice to reveal thepresence of this mysterious bodily haze.

Buried among historical observations and

A sketch of a room, outlining conditions under which the human aura is best viewed.

tion. Unfortunately, the book was allowedto go out of print, Kilner died and fewscientific workers attempted to repeat andadvance his experiments.

WINDOW BLINDDRAWN DOWN

flCLEAR WINDOW SPACE

DARK CLOTH DRAWN UPOVER LOWER PORTION

OF WINDOW

Obtaining the correct lighting conditions for viewingthe aura. The window of the room should be darkened

in the manner shown.

facts are to be found records of individualsaround whose bodies has been witnessedluminous mists. The halo surrounding the'head of the saint is traditional and may,

without much doubt, have a basis of actualfact. In modern times the halo aroundthe human head has come to be regardedpurely as a symbol of sanctity. Records of

holy persons who in life actually went aboutwith their heads surrounded by a luminoushaze are supposed to exist. One has noright to assume that such records are false.Under certain conditions it has beenexperimentally demonstrated that thehuman aura can shine forth so as to becomealmost visible in daylight. May it not be,therefore, that a life associated withausterity and mystical contemplation canbe accompanied at times by so great anamplification of the bodily aura that thelatter becomes visible about those areasof the body-chiefly the head-which areunclothed ? Mysticism and sanctity havebeen proved to be productive of far moreremarkable phenomena than the generationof outwardly visible auras.

Be that as it may, however, the matterin which the present reader will mainly beinterested is that of seeing the human aurafor himself. That the aura can be seen underquite simple experimental conditions thereis no doubt. Nevertheless, the reader whothinks of taking up experiments in thissubject is warned that such experimentsmay possibly lead to disappointments. Ina word, the amateur aura investigator, afterobtaining the necessary materials, may find



that he is unable to hit upon the preciseexperimental conditions for the success ofhis experiments. He may even find thathe is one of those individuals whose eyesappear to be totally insensitive to the aura'srays.

ExperimentsIn order to make experiments in the

viewing of the aura, a certain dyestuff is

I

I

1 '

I

,

.4. .4..dr

\

\ /

I;

I

(Left.) The aura of a healthy man, and (right) a sideview of a boy's aura.

required. This dye is known as dioyanine.Unfortunately, it is a very expensivedyestuff. Just after the war the dye wasbeing produced in minute quantities at acost of £6 per gm. It can now be had ata very much reduced price through anywholesale house of manufacturing chemistsor laboratory suppliers. Dicyanine is madeby the firm of Meister, Lucius and Bruning,of Hoechst, Germany. It is also manu-factured in the laboratories of the Ameri-can Kodak Company at Rochester, N.Y.,U.S.A.

Experimenters who contemplate obtain-ing a small quantity of dicyanine should becareful not to confuse this dye with" Dicyanine A," which is not the same asdicyanine and which is not suitable for thepurpose.

In order to witness the human aura, theinvestigator first of all " sensitises " hiseyes by looking through a liquid light -filter or screen composed of dicyaninedissolved in pure alcohol. Immediatelyafterwards, the experimenter gazes throughanother dicyanine screen at the " subject,"who stands partially or totally unclothedagainst a suitable background. Completelysurrounding the body of the subject, or, atleast around that portion of the bodywhich is unclothed, is then seen a faint,hazy, cloud -like aura, usually of a greyishhue, but varying frequently in colour, whichfollows roughly the outlines of the body andextends to about a foot or so away from thebody.

The aura can often be separated intothree distinct portions. Nearest to the bodythere may sometimes be seen a narrow andalmost transparent band following thebodily outlines. This Dr. Kilner termedthe Etheric Double, on account of its beingthe exact shape of the body. Next to the

etheric double comes the Inner Aura, thestrongest and plainest of the three auras,and, after this, the Outer Aura, which is themost distant from the body and which fadesaway imperceptibly into space. Thesethree portions of the human aura blendtogether very finely, making it often difficultto distinguish their lines of demarcation.

The action of the dyestuff, dioyanine,upon the retina of the eye is not known.In some peculiar manner it appears toconfer a temporary sensitivity upon thelight -receiving elements of the retina. Ithas been suggested, on the contrary, thatdicyanine works in an opposite manner,that is to say, by actually decreasing theretinal sensitivity of the eye to certainwavelengths, thereby subduing that portionof the spectrum whose wavelengths norm-ally overpower and block out the faint raysproceeding from the aura. This supposi-tion, however, for many reasons, is difficultto accept in its entirety.

A Dicyanine ScreenA dicyanine screen is not easy to make.

In its most perfect form it comprises twopieces of fiat (preferably optically worked)glass cemented together with glass separa-tors between them so as to form a liquid -tight cell. A good substitute for such a cellis a small flat -sided bottle. Such a bottlecan be procured from any chemist's shop.It should be of small dimensions, otherwisea large quantity of the expensive dicyaninesolution will be required to fill it. Such abottle will suffice amply, provided it istightly stoppered or corked, for the " sensi-tising " screen whose function is explainedlater. For the " viewing " screen, however,a more suitable cell is re-quired. This must haveperfectly flat sides, for ithas to act as a visual screen,and thus any irregularitiesin its sides would give riseto much distortion. Asmall perfume bottle, flatsided and well stoppered,will often meet the aboverequirements. Better stillis an "animalcule trough,"which is a small glass -walled trough used for thepurpose of confining smallliving aquatic creatures formicroscopical observationsand which may usually beobtained from any labora-tory supplier or dealer innatural history requisites.

Dicyanine must not bedissolved in water. Itsaqueous solution decom-poses very rapidly, and thiswould result in a wastageof the valuable dye. Di-cyanine is best dissolved inabsolute alcohol (not recti-fied or methylated spirits).Unfortunately, the price ofabsolute alcohol in thiscountry is, on account ofexcise duty, in the prohibi-tive region of 27s. per lb.A good substitute for it,however, is iso-propyl al-cohol, which is not subjectto duty and which costsabout 4s. per lb. Half apound of iso-propyl alcohol, or even less,will be amply sufficient for numerous auraexperiments.

For viewing the aura, two dicyaninescreens must be made up. The first is madeby dissolving sufficient dioyanine in thealcohol to produce a solution of a strong

blue coloration. This is poured into theflat -sided bottle or other suitable glass cell,and it constitutes the " sensitising screen."A much weaker alcoholic solution ofdicyanine solution is now made up, the tintof the solution in this case being merely apale blue. This is poured into anotherflat -sided bottle or liquid -holding cell, and itthen comprises the " viewing screen."

The aura is best viewed in a small roomhaving a single window fitted at the topwith an ordinary opaque roller blind andhaving at the bottom an extra blind orcurtain of black material which can beraised to any required height, thus forminga slit between itself and the upper blindthrough which light can enter the room.The subject of the experiments standsstripped or partially stripped opposite thewindow. Behind him is placed a plainbackground. The colour of this back-ground is usually immaterial. Someobservers have preferred a perfectly whitebackground; others favour a greyish one.The latter is probably the best for mostaura viewing purposes.

The actual lighting of the subject is ofgreatest importance. The light should bearranged through the slit formed by thetop and bottom window blinds so that thesubject's body is just clearly visible. Toostrong a lighting will, by its sheer intensity,flood out and overpower the aura, makingits viewing absolutely impossible. On theother hand, if the lighting is too dim,attempts to peer through the gloom at thesubject will only result in optical fatigue.

Viewing the AuraThe actual manner of viewing the aura,

A small flat -sided bottle filled with dicyanine solution being used as asensitising screen for the eyes.

the above conditions having been compliedwith, is simple. The experimenter takes upthe dark blue " sensitising " dicyaninescreen, raises it in front of his eyes and looksthrough it at the daylight sky through theslit in the window blinds for two or threeminutes. Brilliant sunshine should not be



viewed through the screen. It is un-necessary and only injures the sensitisingproperties of the screen.

The eyes having been sensitised in theabove manner, the experimenter turns hisback to the window, puts down the " sensi-tising " screen and takes up the " viewing "screen. He looks through this at thesubject, who is standing against the plainbackground at the opposite side of theroom. If the eye sensitisation has beensuccessful, the aura will be seen imme-diately around the naked portions of thesubject's body.

Since the peculiar effect on the eyes ofthe dicyanine screen is cumulative, repeatedgazings through the sensitising screen maybe necessary before the aura is first seen.Once the aura has been discerned, however,the necessity for previously looking up atthe sky through the " sensitising " screenwill become progressively less and less.With some individuals there will come atime when a mere glance through the" sensitising " screen beforehand will sufficeto confer the necessary sensitivity upon theeyes for the perception of the aura. Suchpersons, also, will find, in time, that theycan perceive the aura without having tolook through the " viewing " screen at thesubject of the experiments.

It may be as well to utter a caution here.It has been reported that, in some instances,too prolonged gazing through the dicyaninesensitising screen has proved injurious, in atemporary manner, to the eyes. If, there-fore, any strain on the eyes is experiencedafter repeated applications of the dicyaninesensitising screen, the experiments shouldbe terminated for the time being.

Dicyanine is not a very stable dyestuff.In water solutions it decomposes rapidly,and even in alcoholic solution its keepingqualities are not good. In the presence oflight, dicyanine solutions are particularly

unstable. This is probably due to the factthat the dicyanine of commerce is not apure dyestuff, but that it is a mixture ofat least three closely allied and difficultlyseparable blue dyes. The action of lightinitiates complex reactions between thecomponent dyestuffs of commercial di-cyanine. Hence the instability of theproduct. Do not, therefore, make up moredicyanine solution than is actually neededat the time. Once made up, the dicyaninesolution should be kept in total darkness,except when it is actually in use. Thisprecaution will slow down the decomposi-tion of the dyestuff very considerably, and,under these conditions, the dicyaninesolutions will retain their sensitising powersover a period of weeks instead of days, aswould otherwise be the case.

Any scientific investigator who takes upthe systematic study of the human aurahas a rich field of research in front ofhim. Unfortunately, however, there appearsto be a " personal factor " present in thematter which makes it apparently impos-sible for some individuals to witness theaura. This inhibiting factor may bepresent in as much as 40 per cent. ofindividuals, even when their eyes have beensensitised by prolonged gazing throughfreshly made dicyanine screens.

The use of the expensive dicyanineappears to be necessary to aura viewing.One or two workers have claimed thatmethyl blue (not methylene blue) possessessensitising properties which enable the aurato be seen. Perhaps, therefore, this rela-tively cheap dyestuff (costing about 2s. per

oz. in purified form) may be worth atrial. It can be used in water solution,since it is perfectly stable.

Its Nature UnknownThe precise nature of the human aura is

unknown. It may be some obscure electro-

optical effect consequent upon the livingforces of the body. More probably, however,it is some form of heat emanation arisingfrom the body. It would not be advisableto say that the aura cannot be photo-graphed. Rather, it should be stated thatthe aura has, up to the present, not beenphotographed, despite many attempts atthat feat.

The existence of this shadowy emanationaround the body is not, after all has beensaid and done, very surprising. Many otherthings possess their own characteristicauras or fields of influence. Atoms have theirown circumscribed attractive fields. Thelines of force surrounding a magnet arewell known. So, also, is the electro-magnetic field which surrounds a wirecarrying an electric current. That theliving organism, therefore, should possess aghostly emanation which is visible undercertain conditions is not a very startlingobservation, despite the enormous interestattached to.it. More likely than not, it will bediscovered, in time, that every living creaturepossesses a characteristic aura of its own.

The present problem, however, is toelucidate more fully the exact nature ofthe human aura, to determine more pre-cisely how it varies with individuals ofdifferent ages, sexes, states of health andconditions of mind. Moreover, it would beexceedingly advantageous if the dicyaninemethod of viewing could be done away withand if some cheaper and better meansof witnessing the phenomenon could beprovided in its place. For, after all, thedicyanine method of aura viewing, which,as we have seen, has about a 40 per cent.failure factor is not a very satisfactorymethod, and the writar of this article wouldadvise readers to bear this fact in mindbefore deciding to embark upon the purchaseof the expensive dicyanine for the purposeof such trials.

Seen at OlympiaTHE official scale model of the Cunard -

White Star liner Queen Mary was seenby the public for the first time at the

Ideal Home Exhibition.The model, 5 tons in weight and 24 ft. in

length, is a perfect model of the liner andsimilar in every detail to that used atClydebank to reproduce in advance theactual launch of the vessel by the Queen lastSeptember.

Only at the Exhibition did the Cunard -White Star Company feel safe in allowingthe model to be shown, for marine engineersall over the world have tried in vain to dis-cover the secrets of the world's greatest ship.

The model, in a 26 -ft. glass case, wastransported to Olympia on a speciallydesigned railway truck, from which it wasremoved in London and towed by road-aspecial precaution taken so that the glasscase was never removed and nobodyactually handled the model.

The model was shown on the first floorof the Empire Hall with two reproductionsof Cunard -White Star liner cabins.Twenty-five Years of Progress

AFEATURE of supreme interest to themechanically minded was a review of theamazing progress of invention during

the King's reign. By the co-operation of theMarconiphone Company, much of the earlyexperimental equipment of the MarcheseMarconi was on view. The developmentof the gramophone from the early typewith external horns to the handsome highfidelity autoradiograms of to -day, contain-ing fifteen valves and more than 6,000 parts,

ITEMS OF INTEREST

and the advances in sound -recording wasshown by the H.M.V. Company.

Fascinating exhibits illustrating progressin building and in the technical equipmentof the G.P.O. was opened to inspection,and the newly -formed National League ofAirmen provided a display of universalinterest.

Elsewhere, a £50,000 installation of thevery latest types of British canning machineshowed the new industry peeling, coring,slicing, boiling and canning fruit almost asfast as you could eat it.

For garden -lovers there was all the thrillof a peaceful, sunny " world tour " througha wonderland of beauty that was a joy tothe eye-the Gardens of the Nations. AChinese " Moon " garden made for lovers,a Japanese retreat in the shadow of Fuji-yama, a haunt of beauty by an Italianlake-these were but a few of the enchantingscenes from Holland, Germany, Spain, NewZealand, and many other lands reproducedfor the public's delight by some of Britain'sfamous landscape artists.

Model " 00 " Gauge RailwayFOR some time past we have included

articles giving constructional detailsof indoor model railways of the " 00 "

gauge, which is the most adaptable indoorsize, and quite a good layout with stations,goods yards, etc., can be got into quite a

small space. It was with interest that weaccepted an invitation from Messrs.Hamblings, who are the specialists in thisgauge, to inspect their showrooms, and wewere amazed to see the wonderful range ofmodels now available. We understand thatthere is an ever-growing interest in this newgauge, and a look round Messrs. Hamblings'showrooms certainly convinces one of thefascination of these small scale models.There are locomotives in perfect detail, allelectrically controlled, wagons, vans, infact, every type of rolling stock all withdetail and to scale. A complete model ofthe Southern electric train is very attractive,and it is surprising the amount of correctdetail, that can be achieved and can bedone by the home constructor. Messrs.Hamblings give practical help to customersboth for construction of models and alsothe electrical circuits necessary for thecontrol.

It is really fascinating to see a loco moveback on to coaches, automatically couple,and haul them out of the station and detachagain ; or, again, a small tank loco doingshunting in a goods yard, picking upwagons and releasing them, all at the willof the operator without having to handlethem.

We recommend interested readers tovisit Ramblings at 26 Charing Cross Road,London, W.C.2. There is no obligation topurchase ; just call and see these models ; orthey will be pleased to send full lists and asample of the track so that you can see thesize, noting that the running rail hascorrect bull -head section, even in this smallgauge.



Model Electric Railways No. 2

SECTION 7

secnori 16

By E. W. TWINING

An Automatic Control and Signalling SystemFEEDER CA&

rEt0611 CAM!

Fig. 4.-A set of points for double lines arranged for automatic working.

S

S was stated in connection with Fig. 1,the system is precisely the same forboth up and down lines in a double -

track railway, but where points occur to abranch in double -track, although exactlythe same relays are used, additional con-tacts are required. Thus, as the purposeserved by these will be dependent upon thestate of the tongue of the points-i.e.,whether open to the main lines or thebranch lines-the contacts must be operatedwith the tongues and are so placed thatthey are moved by the point -operating rodsor mechanism.

Requirements for Working of TrainsBefore going into the details of contacts

and connections, it is necessary to considerwhat is called for in safeguarding trainstravelling to and from main and branchlines, over the points on both up and downrails. These may be stated as follows :-

(1) The passage of a train over thepoints on the DOWN MAIN line must cut outcurrent from the UP BRANCH line. Similarly,an UP BRANCH train must cause the DOWNMAIN line to be dead.

(2) The passage of an UP BRANCH trainmust cut out the section which includes thepoints and stop an UP MAIN train, or

- (3) The passage of an trr MAIN train mustcut out and stop an ur BRANCH train.

(4) A train on the DOWN BRANCH line inthe section ahead of and which includesthe points must permit a train to proceedover the points on to the DOWN MAIN line.

(5) A train standing on the DOWNBRANCH line must not stop an UP BRANCHtrain.

(6) It will be in the power of the personat the control panel to send a DOWN traineither to the BRANCH line or to the MAINline by operating the points accordingly,but the Air LINE points, which are trailing,

they are worked from the control panel,will, if they are set for an ur MAIN train,stop an UP BRANCH train, and vice versti.They can, however, be made to operateautomatically, being moved and set by, andfor, the first train to enter either of thesections approaching the points, thoughthis has not been provided for in the scheme.

Diagram of Points and CircuitsThe lay -out of a double set of points to

main and branch lines is shown in Fig. 4.In this is included the relays controllingthe block sections on either side of thepoints, with the additional contacts on thepoint rods already referred to.

With the diagram before you, considerhow the conditions for safe working arecomplied with : it being taken for grantedthat the conditions are obviously neces-sary. They are dealt with in the ordergiven above.

Compliance with Conditions(1) This is complied with, not by the

actual passage of a train entering section 8(see diagram), but by the setting over of

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the points for the nowN MAIN line. Thecurrent supply to the third rail of section 15will be interrupted by the opening of thetwo contact leaves A on the point rodswitches. Through these leaves, the currentis passed viii the leaves E on the DOWNpoint rod switch, via the contact onrelay 14-15 and from the feeder cable.Should the DOWN points be already setover the other way-i.e., for an UP MAINtrain on section 14-the switch A will haveno effect, since the DOWN BRANCH line,third rail, section 15, will be already cutout by switch leaves E.

The second condition in (1), which pro-vides that an ur BRANCH train shall stopa DOWN MAIN, is complied with by causingthe third rail of section 7 to carry nocurrent. This third rail is cut out by itsown relay No. 7, the coil of which derivescurrent thus : from battery through railNo. 1, through wheels and axles on section15, through second rails of this andsection 8, through switch leaves D2 and D',through coil of relay 7 and 144 feeder tobattery. Should a DOWN train be approach-ing on section 7 which is intended for thebranch line it will not be stopped by anUP BRANCH train because the points willbe set so that switch leaf D2 will be in-operative and only a train on DOWN linesection 10 will cause the train in section 7to pull up.

(2) An UP BRANCH train will stop anUP MAIN train or (3) vice versa, through themedium of switch leaves E, according tothe position in which the points are set.If the points are as shown in Fig. 4 thecurrent path is broken to the third rail ofsection 14, and flows to section 15. Iftrains enter sections 14 and 15 simul-taneously, one of them will be stoppedaccording to the point setting. It ispossible, therefore, by setting points early,



for the operator to give the preference towhichever train he wishes, even though onetrain be before the other.I (4) In order to render this impossible,the point tongues of the second rails mustbe interrupted or insulated. It will be seenfrom the diagram that if they were notinsulated, when a DOWN BRANCH train wasstopped in section 10, or for some reasonhad not cleared the section, and a followingtrain wished to pass to the DOWN MAIN-section 8-it could not proceed even whenthe points were set over for it, because thepoint tongue would put the second rail ofsection 10 in connection with that ofsection 8 and the switch leaf D2 would beinoperative. Consequently, the third railsof sections 7 and 8 would remain deadthrough relay 7 remaining energised. Withan insulated point tongue, even if a train isin section 10, the opening of the points tothe DOWN MAIN line changes over switchtongues D1-3 to D1-2, which causesrelay 7 to open and restore current to boththe third rails.

(5) Here again the insulated pointtongue leading to sections 8 and 10 isutilised to prevent this occurring. If thetongue was not insulated and the pointswere put over to the opposite position tothat shown in Fig. 4, immediately after thepassage of a DOWN BRANCH train an UPBRANCH train, on entering section 13, wouldbe stopped because relay No. 13 would beactuated in just the same way as it wouldif section 15 were occupied.

(6) The automatic starting and stoppingof the up trains in sections 15 and 14 iscontrolled by switch leaves E according tothe state of the tongue of the points.

The foregoing will doubtless provide anadequate description of the general arrange.ment of the rails, relays and electrical con-nections and it only remains to refer to thesignal lamps before passing on to the designof the point -operating gear.

Signal LightsIn the ordinary way the lamps, marked

R and G in the diagrams for Red andGreen respectively, are controlled directfrom contacts on the relays, but at thepoints on the DOWN lines the lights have,of course, to be doubled, one pair for thedown main and one pair for the downbranch. The control of the lighting ofthese must be with the points and soadditional switches B and C are introducedon the point -rod gear. When the pointsare open to a branch train the left-handgreen light and the right-hand red lightboth glow, and vice versa.

Point Operating GearThe point tongues are moved by solenoids

-coils having sliding cores-a pair of thembeing inter -connected mechanically. Thewhole arrangement is shown in Fig. 5,including the electrical switches shown inFig. 4. It should be made clear that thenumber of switch springs or leaves hereshown are those required for the DOWN

facing points, A, B, C and D, shown inFig. 4. For the uP trailing points only thethree leaf contacts at E, Fig. 4, will have tobe fitted. The automatic locking of thetongues, after being moved, is provided forby the form of the ends of the slot in theplate connecting the cores. These slot -endsbeing parallel with the direction of motionsecurely hold the lever which actuates thepoint rod. Each coil of the solenoidsshould be wound with 4 oz. No. 22 orNo. 24 enamelled wire on brass bobbins andhoused in casings of soft iron plate, asshown. The base plate and brackets maybe of either brass or aluminium.

The rest of the details will be obviousfrom the drawing ; the reader is asked toremember, however, that the two pointtongues must be insulated one from theother and it is therefore important that therod inter -connecting the two tonguesmust have an adjusting turnbuckle madeof red fibre. The rod ends will bethreaded right and left hand, and mustnever be screwed up sufficiently to makecontact.

Obviously, connections to the coils of thesolenoids for working them will be takenfrom the control panel of the railway, wherea two-way switch will be fitted. Threewires will be run, one of them common toboth coils.

A scheme for the automatic operation ofthe points by the trains themselves is not avery complicated matter and this will bedealt with in the next article.

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Fig. 5.-Point operating solenoids with switches for automatic working.



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This Spring, we celebrate the 25th anniversary of ourregistration as a limited company, and, in honour of this,have prepared a specially fine series of spring boats, all ofwhich are described in our NEW SHIPS CATALOGUE, S.I2.Yachts like " Endeavour " and our new " Southwold " racer,cabin cruisers like " Margaret Rose " and motor boats like" lolanthe " and the 2I/- " Raleigh," and best of all our newspeed boat " Streamlinia."Make your choice from this wonderful array described in ournew Ships Catalogue S.12, published this month. Modelmakers will find new sets of parts and fittings in NEW S.12,price 6d., post free. Send for your copy now!

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Rawlplugs enable anyone to make firm fixtures in brick, con-crete, stone, tile, plaster, etc. The old method of usingunsightly nails or ugly wood plugs is never satisfactory,because they always work loose. The Rawlplug method isfar neater, stronger and firmer, and no damage is done towalls or decorations. Complete Outfits i/6, 3/6 and 5/6.Rawlplug DU ROFI XThe Heat & Waterproof AdhesiveRawlplug Durofix is the most effectiveof all adhesives by reason of its greatstrength. It will withstand boiling wateror the heat of an oven. Durofix is theideal adhesive for Sportsmen, becauseonce dry it will not become tacky again.Sold in big orange tubes, 1/-. Smallersize, 6d.B. lea The Rawlplug Co. Ltd., Cromwe II Road, London, S.W.7

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UP-TO-DATE : AUTHORITATIVE : PRACTICAL

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GEORGE NEWNES LIMITED8-11 Southampton Street, Strand, London, W.C.2



°

A Vest Pocket Exposure MeterMEASURING only -I in.,

the Leudi vest pocket exposuremeter shown below is one of the

smallest and lightest extinction photo-meters made. It has no lens, needs nofocussing, no reference to tables, is aseffective indoors as out of doors, and canbe used with plates or film of any make.

The brightness of the subject can beinstantly seen ,by looking through thecentral opening of the device. A series ofnumbers, varying in density, is observed,and the last clearly visible number is takenas the guide. This number is then broughtover the square space on the meter corre-sponding to the light prevailing. Thecorrect exposure will then be found oppositethe lens aperture to be used. The metercosts 5s. [116.]

1 Y2Vre

" 1A.0

9 lito12

116

1$

23 1

36

The Leudi vest pocket exposure meter, the size ofwhich can be gathered from the photograph on the

right. It is sold by Sands, Hunter, Ltd.

A New Type of Suction PlugANEW type of bathroom or hand -basinplug is that shown below, which is held

in position over the outlet by means ofwater pressure. When fitted into place, itis claimed that it cannot be accidentallydislodged. Obtainable with a chromiumplated finish, it costs 2s. [117.]

Safeguard Your Wireless SetA FUSE plug has recently been

/-1intro-

duced by a well-known wireless firmwhich is interchangeable with all standard

5 -ampere, 2 -pinplug sockets. Ithas a cartridgefuse incorporated

A suction plug for thebath or hand -basin which carvrt be accidentally

dislodged.

The address of the makers ofany device described belowwill be sent on applicationto the Editor, PRACTICALMECHANICS 8-11, Southamp-ton St., Strand, W.C. 2.

Quote number at endof paragraph.

in each pole which blows at approximately 2amperes, thus in case of a short-circuit thefuse blows in the plug, and can be promptlyreplaced at a negligible cost. The combinedbase and plug is also obtainable providedwith a milled nut and screw, which enablesthe plug to be fixed to the base to preventits inadvertent withdrawal. The price ofthe plug base with plug top, locking nut andscrew is ls. 10d., a twin fuse plug completewith two fuses costs ls. 4d., a 5 -ampereplug base costs 6d., and extra fuses cost 4d.each. [118]

The " cosy " draught excluder which can be fitted tothe bottom of doors, French windows, etc., in a few

minutes.

The " Cosy " Draught ExcluderDHAUGHTY doors and windows are a

bugbear in most households. A simpleand easy method of overcoming thisdifficulty is to fit the "cosy " draughtexcluder shown on this page. Two typesare shown in the sketch, one for the bottomof doors and the other, known as " Cosy T,"for double doors, Frenchwindows, the tops ofrise and fall windows,motor -car floor boards,etc. As can be seen,the two sides of the" Cosy T " are of adifferent width, to allowfor fitting to wide ornarrow apertures. Bothtypes are made ofrubber reinforced withcanvas, the former cost-ing 6d. per foot and thelatter 31d. per foot.[119.]

Arnold Stop WatchesWE have recently

had the pleasureof testing a moderatelypriced thirty -hour stopwatch, which has

recently been placed on themarket. Costing only 10s. 6d.,it is wonderful value formoney, and there is a threeyears' guarantee with eachmodel. The same type ofwatch is also available as awrist watch and costs 158.complete with strap.

Furthermore, so that readersmay judge the demand forthese watches, the manufact-urers, Messrs. A. Arnold & Co.,are willing to let readers havethem on a sale or return basis.[120.]

The Brush Grille -type Micro-phone

THE Brush grille -type micro-phones consist of various

designs of cases all constructedof monel - metal containingsound - cells arranged, asimplied, in the form of a grille.Monel-metal is used for the sakeof appearance and resistance tocorrosion. The microphonesare extremely robust, and areunaffected by sudden tempera-ture changes. They are alsoextremely compact. The small-est weighs but 2 oz., and thelarger models, complete withsocket, weigh only 12 oz.

It is almost unbreakable,having no delicate mechanicalparts, is unaffected by vibra-tion or shock, and cannot beover -loaded. Having only twoconductors (there is no fieldcurrent or polarising voltage),it provides complete freedomfrom background noise. -[121.]

A Popular Sculling Exerciser

Showing theBrush grille -type micro-

phone.

THE sculling exerciser shown belowhas been designed to meet the demand

of a good -class exerciser at a popular price.Its smooth gliding action-a good reproduc-tion of actual sculling-tones up themuscles, reduces surplus weight andassists the building of normal healthytissue. The standard models have steeltube frames, centrally divided for packinginto a small space, a comfortable slidingseat and fibre silent rollers. The strengthof pull on the rope springs may be variedby using one, two or three springs. Thechassis is black enamelled, and the steel -strands, clips and pulley blocks are chro-mium plated. It is 5 ft. 5 in. in length,weighs 201 lb., and may be fitted with a

rocker chassis as shown, ifdesired. The price is 84s.with an enamelled chassis,110s.with a chromium platedchassis, and the junior modelcosts 63s. The standardrocker chassis is 15s. 6d.extra, and the junior rockerchassis costs 108. 6d. [122.]

1

The Terry sculling exerciser.



A Review of the Latest Devices for the AmateurMechanic. The address of the Makers of the Items men-tioned can be had on application to the Editor. Please

quote the number at the end of the paragraph.

THE" Simplex " press, shown below,

should certainly make its appeal tothose readers who like their address em-bossed on their notepaper and postcards.It is fitted with patent adjustable paperguides (top and side), thus enabling theexact stamping position desired to be

ADJUSTABLE GUIDES

The " Simplex " press for embossing notepaper andordinary postcards.

instantly obtained and maintained. Thepress embosses paper with the slightesttouch and postcards with an easy pressure.Fitted with a 24 in. die it enables longaddresses to be properly displayed. Madein various styles the prices range from48. 11d. to 12s. 6d. [124.]

A Universal Electric Grinder and PolisherTHIS universal electric grinder and polisher

will prove ideal for workshop orhousehold use, being suitable for grindingworkshop tools, knives, scissors, etc., andshaping small castings. Fitted with a

The " Seco" universal grinder and polisher.

bristle brush it will polish cutlery, jewellery,plate and all small metal articles, and canalso be used for polishing boots, shoes andleather. The outfit consists of a glo- h.p.high-speed universal ball bearing motor(10,000 revolutions per minute), mountedon a wooden stand with a switch, flex andplug, one 24 in. grinding wheel (4 -in. bore)on a steel arbor. and one 3 -in. polishingmop and taper -threaded arbot.The motor escap-able of drivinga 34 -in. grind-ing wheel, a fanblade or a watchmaker's lathe,and is suppliedfor all standardvoltages, A. C.or D. C. Theprice is 50s.complete, but ahigh-speed 3 -ft.flexible shaftiorthe above witha chuck andtwo collets fordrills (capacity0-4 in.), costs30s. extra.[125.]

The Cooper Stewart speedometerfor fitting to bicycles, which wasdescribed on page 335 of last

month's issue.

The " Bahco " Adjustable SpannerADJUSTABLE in a few seconds and fitted

at one end with a pipe wrench, I in. toin. diameter, theispanner shown on this page

The " Bahco "spanner which canbe adjusted forwork in a few

seconds.

should prove ideal for the home mechanic.The range of the jaws of the spanner is

in. to in. The size of the spanner is24 x 8 in. overall. It costs 4s. 6d. [126.]

A Vacuum Cleaning and Polishing OutfitMESSRS. Brown Brothers Ltd.. have

recently sent us details of the "Supreme"Electric Vacuum Cleaning and PolishingOutfit which they are marketing. Threemachines, which may be bought separatelyif desired, make up the outfit and comprise :

The first is the " Supreme " FerretElectric Cleaner, which is a small, portablemachine which dispenses with hose attach.ments. It is particularly suitable forcleaning the upholstery of the car, and hasinnumerable uses in the home. A rubbernozzle is fitted to obviate scratching thefurniture. A special sprayer is includedfor scent, disinfectant and so forth, and ablower for removing dirt and dust frominaccessible places.

The second is the " Supreme " De LuxeFloor Model. The double suction powerof this machine removes all surface anddeep -trodden dirt from carpets and rugs.Fitted with a safety automatic switch, thecurrent is switched on and off as the machineis used, thus providing a saving in power

cost. The extra wide nozzle saves a greatdeal of time.

The third is the " Supreme " ElectricFloor Polisher. The rapidly revolvingbrush or pad creates a lasting and beautiful

The" Supreme" electricvacuum cleaning and

polishing machine.

surface in a few moments. Simple to use,it only needs guiding.

In addition to a co-operative local dealeradvertising scheme, special hire-purchaseterms are appliable to one or all of theseCleaners and full details and illustratedliterature are available on request. [127.]

A Powerful Concentrated LightTHE " Localite " Arm, illustrated on

this page, gives a perfect concentratedlight with the maximum economy incurrent. It assists mental concentrationand prevents headache and eyestrain. Itcan be placed in any position, as it is fittedwith universal friction joints, and is finishedwith a glossy black stove enamel that isserviceable and durable. The " Localite "Arm is fitted with a " Q " screw -down base,lampshade switch, lampholder and 2 yd.of flex, with a combined wall -plug andbayonet -adapter. The lamp, complete,costs 20s., but is also obtainable for 1 ls.each with only a " Q " socket and withoutthe shade and electrical accessories. [128.]

ErratumOWING to a printers' error, a mistake

occurred in Messrs. Beck's advertise-ment on p. 338 of last month's issue. Theprice of their special parcel of chemistryapparatus, containing 1 flask, flat bottom150 c.c., 1 beaker, spouted 100 c.c. ; 3test tubes, 4 x in. ; 1 thistle funnel 20cm. ; 3 ft. glass tubing, 1 rubber cork 2boles : 4 in. rubber connection tubing and1 glass stirring tube, appeared as 62s., postfree. This, of course, should have been2s. 6d., post free.

The " Localite armwgives a perfect concentrated lightwith the maximum economy in current.



V

Winding a 12 -slot armature. Wire No. Ithe back of No. 121, etc.

T. P. (Aspatria).-Your armature andwindings are not at fault, so do not try torewind, as the results will be worse thanbefore. It is the permanent magnets thatare defective, and they must be re -energised.

H. B. (Devon).-If your landlord is the" Supply Company," then legally you canopen the meter, but once open, the makerswill not be responsible for same or itsbehaviour.

B. H. (Lee).-For a 50 -watt heater suit-able for your tank, you will need 121 yd. ofNo. 40 nickel chrome bare resistance wire.as supplied by Messrs. Grafton Electric Co.

J. B. (Ryton - on - Tyne).-The runningwinding must consist of 170 turns of No. 22D.C.C. wire spaced out on each pole, givinga total of 680 turns for the machine. Thestarting coils consist of 70 turns of No. 30D.C.C. wire. If you have difficulty ingetting all this wire into the slots, connect aseries resistance with the starting coils.

E. S. (Catford).-You cannot get Ile h.p.from your machine if you run it continu-ously. Rewind the armature as for low -voltage D.C. with No. 20 D.C.C. wire,putting on as many turns as possible. Thefields are wound with No. 28 D.C.C. andconnected to give alternate poles.

R. M. (Llandyssil).-A circuit diagramhas been posted to you suitable for boththe experiments.

C. S. (Holt Fleet).-If your draWings arecorrect, the machine when rewound couldnot supply more than 200 watts.

H. B. (Bradford).-The following resist-ance will pass 8 amperes at 230 volts whenusing 1 -in. carbons : 54 yd. of No. 18 bare" Eureka " wire. Wind the wire into 1 -in.spirals.

is connected at

Se.4/4:1 Aie4cAe/Ne!

A-oRce (70,POu4t-o-

SOME ELECTRICALQUERIES ANSWERED

[BY THE TECHNICAL STAFF]

M. C. (Galway).-To design a4 choke you would have to make

a complete study of alternatingcurrents, and a single book wouldbe of no use. The only power achoke absorbs, in theory, is due toits own resistance.

P. P. (Hull).-Sensitive relaysare difficult to make, and aregenerally of the moving -coil type.Your best plan would be to adaptan old moving -coil voltmeter.

W. A. (Wool).-There are specialsets on the market consisting of aconverter and a transformer, and

for serious use you are recommended toinstall one of these.

F. R. (Chadwell Heath).-You have madea mistake in making the fields solid. These,as well as the rotor, should be laminated,and made of good quality stampings.

How a wave armatureis wound.

A. B. (Croydon).-Both the thick andthin wire should be removed from the fieldsand then rewound so as to give north andsouth consecutive poles.

T. S. (Northampton).-We have done con-siderable work on making copper -oxiderectifiers, and if present experiments are

(Left

SHUNT MACH/NE

ftsoceto right). Characteristic curves of series,

shunt: and compound -wound motors.

satisfactory, we may publish an article onmaking a complete unit.

C. L. (Brockley).-The effects mentionedare quite common. You will not ruin a

Place an Order with your Newsagentfor " PRACTICAL MECHANICS " to

be regularly delivered

bulb by the method you mention, thoughwith a heavier discharge the glass may bepierced.

N. F. (Northampton).-You must windyour coil with very nearly 4 oz. of No. 47enamelled wire. This will give a resistanceof 52,790 ohms. Adjust the amount to getthe exact resistance you require.

H. B. (Liverpool).-Both methods yousuggest are impracticable. You can, how-ever, connect the fields in parallel andthen put them in series with the arma-ture.

J. A. (Smethwick).-For full details forconverting car dynamos to A.C. machinesyou should consult the June issue of thispaper.

H. M. (Newcastle-on-Tyne).-From themeagre information you supply, we cannotgive definite advice. Rewind the running

4 S 6windings with No. 34 D.C.C. wire, and thestarting with No. 36.

E. W. (Leeds).-You have omitted tomention the depth of the furnace which weassume to be 10 in. The current taken willbe 11 amperes, and must be started with aresistance in series to avoid damage.

E. W. (Stockport).-The dynamo is woundwith the armature either in series or inshunt with the field. Consult the articlein the December issue of PRACTICALMECHANICS on the principles of smallmotors and dynamos.

L. W. (Sowerby Bridge).-Polarity maybe determined with a pocket compass. Thenorth pole of the magneto magnet is placedon the south pole of the magnetiser.

COA6001.41,0MACIWIVe

ect7.2CE TO.QQ14/4"



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Fig. 1.-Showing the finished magnet.

ALIFTING magnet is an electro-magnet which is especially designedto support heavy weights by the

application of a comparatively small electric current. The model described below iscapable of carrying a current from an8 -volt accumulator, with no other resistancein the circuit, without undue heating up ofthe coil, and it is easily capable of support-ing a load of 25 lb. weight, or even more.The materials used are inexpensive, and thework involved is not beyond the skill of theaverage amateur constructor.

Fig. 1 shows the finished article, andFig. 2 a vertical section. The dimensionsgiven can, of course, be varied to suit indi-vidual requirements, and are merely in-tended as a general guide, but every con-structor knows that a great deal of troublecan be saved by working to dimensionswhich have been previously ascertained forhim by someone who has already con-structed a model. The main portions ofthe body of the magnet are shown separatedin Fig. 6.

The MagnetTo construct the magnet, obtain a piece

of iron piping 11 in. internal diameter andabout f in. in thickness. Cut off a shortlength, about j in., and file and polish the

Fig. 3.-Details of the core of the magnet.

Making aLifting

The magnet described in thisfrom an 8 -volt accumulator

circuit and will easily

ends until they are square, flat and smooth,and the finished length is I in. Of course,the appearance is improved if the outsidesurface of the piping is also finished offsmoothly or even enamelled. This portionwill afterwards be referred to as the " ring "(R) in all diagrams and descriptions.

The " core " (C) is made from a piece of!-in. soft iron rod, } in. long, with the endsworked smooth and square. Through thecentre, drill and counter.sink a hole to I take a I -in.countersunk i

--,-n bolt (B.S.F.

..--thread) fitted z with a nut.This hole is, of course,drilled more K ik easily on alathe if the constructor

c 1

Noi

--)d

24

Fig. 2.-A vertical section through the magnet.

is the fortunate possessor of such amachine. D is a disc of -h-in. sheet ironof the same diameter as the outside of thering, and is also drilled in the centre toallow the bolt to pass through it. Theobject of this disc is not only for strength,but also to close the magnetic circuit. E isa similar disc of ebonite or other insulatingmaterial in. thick, also drilled in thecentre to allow the bolt to pass through iteasily. The supporting ring K is made byturning a strip of *-in. sheet iron into aring of about 11 in. diameter with the endsoverlapping and drilled to take the bolt, asshown in Fig. 1.

it is advantageous to construct from apiece of Fin, soft sheet iron anotherdisc (M) of the same diameter as D and E,though this disc is not actually a portion ofthe magnet itself. Drill and tap it to takea stout screw eye (A). If the top of thehole is slightly countersunk, the eye isscrewed a little way through, riveted andthen filed down level with the disc ; thereis no danger of the eye pulling throughunder strain.

Now drill and tap, all together, the ringR and the discs D and E, so that later on



PowerfuMagnetarticle will carry a currentwith no other resistance inlift a weight of 25 lbs.

they may be held together by four round-head 2B.A. fin. screws (S, Figs. 1 and 2).Also drill together the discs D and E toallow the legs of two terminals T to passthrough the holes later.

The CoilThe next job is to wind the coil. This is

carried out on a " former " (Fig. 4), andthis must first be constructed. The dimen-sions of the " former " are such that thefinished coil will afterwards fit snugly intoits proper position, as shown in Fig. 5,which is a " transparent " view of the ring,core, discs and bolt in position.

The centre of the " former " is a piece offin. wood dowelling .111- in. long, with theends truly squared. The discs P, P1 are

141:

Fig. 4.-The former for the coil with the necessaryconstructional details.

made of plywood 1* in. in diameter. Drilla hole through the centre of the discs anddowelling and pass through them a pieceof threaded brass rod so that the whole canbe held firmly together by a nut at the top,and another at the bottom. A hole to takeone end of the wire should be drilled at Fat the edge of the dowelling. Wrap apiece of paper round the dowelling to

. facilitate the removal of the finished coil.The wire required is about 1/ oz. of No. 28D.C.C. copper.

To wind the coil fix the " former " on alathe, a hand drill clamped in a vice, or onany other form of winder such as thosewhich have been desCribed in PRACTICALMECHANICS. Pass one end of the wirefrom the inside to the outside of the" former " through F, secure it and beginto wind the rest of the wire on the " former."

Fig. 7.-Showing the coil wound and tied with threadafter completion.

C I

Fig. 6 . -Showing thechief parts ofthe magnet.

Arrange between the paper and the firstlayer of wire several pieces of cottonthread to allow the coil to be tied up aftercompletion, as shown in Fig. 7. Afterwinding each layer of wire, apply with abrush a strong solution of shellac in methy-lated spirit, which, when it dries, willimprove the insulation and bind the coiltogether. When the " former " is com-pletely filled, allow the coil to stand as longas possible so that the shellac solution maydry off thoroughly, then tie up the threadsof cotton to secure the coil. Unscrew thenuts on the " former," remove the discs,and slip the coil off.

Assembling the MagnetTo assemble the magnet, first pass the

bolt B through the core C and the discs Dand E. Now place the ring K on the top ofthe bolt and secure the whole in position bythe nut at the top of the bolt. The gripwill be improved by a washer below thenut. Pass the terminals through the holesprepared for them in E and D, fasten theends of the coil to them by small nuts andslip the coil over the core C. Now fastenthe ring in position by the screws S. Setthe coil back from the bottom face of themagnet about rya in. and pour round itmelted paraffin wax to improve the insula-tion and to maintain the coil in position.Remove the excess of wax, level it up, andthe magnet is ready for use. Suspend themagnet by K. Connect the terminals of a2-, 4-, 8-, or 8 -volt accumulator to theterminals T of the magnet. Bring the discM near it, when it will be strongly attracted.Hang weights on A, when the lifting powerof the magnet may be ascertained.

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LIVING FOR 200,000 YEARS(Continued from page 375.)

that its animation is suspended, and after-wards to return it to normal temperaturesand to a continuance of life.

If in such manner a man could be cooleddown instantaneously to an exceedinglylow temperature, it is possible that he wouldremain in a state of frozen animationindefinitely. An individual subjecting him-self to a series of such experiences or treat-ments could, as before mentioned, live outhis life of seventy years in snatches whichwould extend over an enormous number ofcenturies.

Life -suspending RefrigerationFor instance, assuming that an indi-

vidual subjected himself to life -suspendingrefrigeration for the first time at the ageof nineteen or twenfy years, he could, bybeing thawed once every 300 years and byremaining in active life for a period oftwelve months during each third century,spread out his seventy years' span to about15,000 years-that is, assuming also that thecontinual refrigeration and thawing didnot weaken his bodily functions during thethaw intervals.

In the same way, a man, by allowinghimself merely three weeks or a month" in thaw " every third century, couldstretch out his seventy years of life over aperiod of 200,000 years, whilst by reducinghis thaw periods still more, say for merely

a few days at a time, his " life " wouldstretch out to incredible limits. Death,when it did arrive, would overtake theindividual in one of his thaw intervals.It would come to him as it does to allnormal livers-by senility, disease oraccident. No longer, after this occurrence,would the refrigeration process be of anyuse. It would, of course, completelyinhibit the dissolution of the body, but,death having overtaken the individual, thebody would never be self -animated again.

Living out one's life by snatches is anotion concerning which little has beenheard. No doubt, for the majority of per-sons, such a method of interrupted livingwould be distasteful, unsociable and evenheroic. The method, however, wouldmake its appeal to the few. Such indi-viduals would enter nationally controlled" refrigeratories," and before entering intorefrigeration they would signify in somepermanent manner the date at which theywished to be thawed and returned to activelife. Naturally, in view of the decidedimpermanence of most human institutions,individuals entering into refrigeration wouldfind it necessary to take many things ontrust. Such considerations, however, donot concern us here. The mere principle ofthe expansion of life by means of refrigera-tion periods has been outlined. Whether,from the standpoint of human psychology,the method, if it ever became possible,would be practically successful is a questionwhich must be left to individual opinion.

IN THE NEWSGiant TelescopeLAST December the 200 -in. reflector

mirror for the new Mount Wilsontelescope was cast at the Corning GlassWorks in America. Watched by experts,it is now being cooled at the rate of 1 degreedrop in temperature per day. Sometimenext autumn it will at last be cooled, andit is hoped perfectly annealed. In the cast-ing of this disc, 2 ft. thick and 17 ft. indiameter, 40 tons of special glass were used.The glass was melted in a furnace at whiteheat (1.580° C.). White heat was main-tained for fifteen days to free the melt fromair bubbles. It was then picked up in750-1b. ladles and poured into the mould.The mould has a honeycomb structureunderneath to give the disc rigidity for theleast weight. In casting it was kept undera gas -heated hood which had doors in theside for the entrance of the pouring ladles.When pouring was finished the gas wasturned off and the disc was allowed to cooldown to red heat. The hood was thenlifted and the mould was traversed away tothe annealing hood. Both annealing hoodand mould have exactly controlled electricheating elements to regulate the coolingto the required 1 degree per day. If thedisc were not so carefully cooled stresseswould be set up in the interior which, ifthey did not cause it to explode suddenlyinto small fragments, would so distort andstriate it that it would be useless for itsoptical purpose. When the disc is finallycooled and delivered to Mount Wilson, itwill then have to be ground to an exactparabolic curvature and silvered over witha reflecting surface of metallic aluminium.These operations will take a further threeyears.Damming a Canyon

SOUTHERN California, in need of waterSOUTHERNpower for electricity, has dammed

a subsidiary gorge of the Grand Canyon inthe Rocky Mountains. Irrigation damshave been built before, as the huge Nilebarrier. But this, the Boulder Dam acrossthe Black Canyon, is something exceptional.A deep, rocky gorge has been filled by asingle poured concrete monolith, 700 ft. inheight, 660 ft. thick, and spanning 220 yd.in a sweeping curve. Seven million tons ofconcrete have been used, requiring thewhole output of four oement factories fortwo years. Curiously, to chemists belongsthe chief distinction in the work. With solarge a single mass of concrete the settingheat given up by the cement could notescape from the interior fast enough. Thecrust sets and cools quickly, confining theheat in the inside, so that it would get over-heated and seriously expand. The combina-tion of hot expanded interior and contractedcrust would crack and weaken the wholestructure. Chemists overcame the difficultypartly by preparing a new type of cementwith only half the setting heat of ordinaryPortland cement and partly by force -cooling of the whole dam. The dam as itgrows is honeycombed with steel pipesleading to headers on the dam face. Re-frigerated water is pumped through thiscooling system. When the job is finishedand set the pipes will be filled full of liquidcement and grouted off.

The giant spillways, pipes 30 ft. indiameter, valves and tees of the powerscheme, as they are too big to bring to thespot, have been riveted up on location in aspecially built steel mills. The cost of thescheme is assessed at £100,000,000.

A STANDARD WORK

Newnes Encyclopmdia of PopularMechanics, by F. J. Camm. 5/- or 5/6by post from Geo. Newnes Ltd., 8/11

Southampton Street, Strand, W.C.2.



MONEY

EVI EWEDBY OURPATENT INERT

AN IMPROVED PAINT BRUSH" I should be pleased if you would tell me

of the commercial value of the three designsI have enclosed.

" I should like to Letter Patent ' thefirst design if possible, and I should be verypleased if you would supply me with informa-tion as to the cost of the process.

" This is the one I am particularlyinterested in, as one firm I know wouldmarket it for me.

" If you think it has any value I shouldbe pleased if you can tell me the names andaddresses of some of the leading paint brushmanufacturers.

" Thanking you in anticipation of anearly reply." (A. B., Bucks.)

(1) The suggested improvement in paintbrushes is thought to be novel and formsfit subject -matter for protection by LettersPatent. It is presumed that the inventorhas practically tried the invention and thatit will in fact do what is claimed for it. Ifso it should have a commercial value which,however, will depend largely on the way itis marketed. The inventor being satisfiedas to the capabilities of the invention isadvised to protect it by filing an Applica-tion for Patent with a Provisional Speci-fication which will give him protection forabout twelve months, during which periodit should be possible to ascertain if theinvention is likely to be commerciallysuccessful.

The following are brush manufacturerswho might possibly be interested in theidea :-

Messrs. Ernest W. Perrett Ltd., 68 EastIndia Dock Road, London, E.14. Messrs.Rigby Battock Ltd., Upper Clapton,London, E.5. Messrs. Hamilton & Co.(London) Ltd., 116 Clerkenwell Road,London, E.C.1. Messrs. G. B. Kent & SonsLtd., 75 Farringdon Road, London, E.C.1.

(2) The improved funnel is apparentlya removable spout for petrol tins, and is notthought to have much chance of being madea commercial success, for the reason thatpetrol is now being increasingly supplied tomotorists by wayside pumps and the useof 2 -gallon petrol tins is rapidly diminishing.

(3) The case for match -boxes to enable acigarette to be readily lit in a wind, isingenious, but is not thought to be particu-larly novel. There have been a number ofPatents granted for match -box cases havingthe same object in view, but none is believedto have been commercially successful. Theextra bulk would militate against theproposed construction, and the idea is notthought to have any large commercialvalue, even if it be capable of being validlyprotected.AN IMPROVED TOWEL HOLDER

" I would appreciate your advice on theenclosed sketch of a domestic article.

" Apart from the novelty and efficiencyof the Idea-I have had one in use in myhome for one and a half years-it is de-signed for mass production, as apart fromthe fixing screws there are only three parts.Could the idea be patented ?

" If not would a design registration allowme to have it manufactured and used com-mercially." (J. L., Newcastle -on -Tyne.)

The improved towel holder is extremelyingenious and should be a great commercialsuccess if properly marketed. It is certainlynovel so far as is known from personalknowledge and forms fit subject -matter forprotection both by Patent and Designregistration.

The inventor is advised to protect theinvention by filing an Application for Patentwith a Provisional Specification, since theprotection thereby afforded is very muchbroader than by registration of a Design.A Design registration only gives protectionfor the article as judged solely by the eye,and it would be easily possible by varyingthe shape or configuration, whilst employingthe gist of the invention, to overcome theDesign registration.

The inventor is advised to file a PatentApplication and then approach manu-facturers with a view to their taking aninterest either to manufacture or market it.The Editor will be pleased to put you intouch with a reliable Patent Agent.

AUTOMATIC WEIGHING MACHINEMECHANISMS

" I would like your advice regarding thetwo drawings enclosed. The first sketch is apatented mechanism for an automaticweighing machine, and the other is themechanism for the same type of machine,but is not patented. What I wish to knowis, if I patent the number two design shouldI be infringing, the number one design."(R. N., Leeds.)

Without having the Patent Specificationcovering the automatic weighing machinebefore us it is a little difficult to advise,but apparently the proposed new arrange-ment is simply the employment of a singlemechanism in place of a dual one usuallyemployed. This being so, it is not thoughtthat the omission of the second mechanismconstitutes invention or subject -mattersufficient to support a Patent. On thepresumption that the specification andclaims of the original Patent have been ablydrafted, there can be little doubt that theproposed arrangement would, if manu-factured, sold or used, be an infringementof the original Patent. The mere act ofpatenting an invention does not constituteinfringement of an earlier Patent, as theApplicant seems to imply. A valid Patentcan be obtained for an invention and it isonly when the said invention is manu-factured/ sold or used, that infringementwould ensue.

THE ENCYCLOPAEDIA OF'POPULAR MECHANICS

By F. J. Camm

392 Pages, 627 Illustrations

5/- or 5/6 by post from Geo. Newnes Ltd.,8/11 Southampton Street, Strand, W.C.2.

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If a postal reply Is desired, a stamped addressed envelopsent must bear the name and address of the sender andcover. Send your queries to the Editor, PRACTICAL

Street, Strand,

MAKING HYDROGEN PEROXIDE" Can you tell me how to make hydrogen

peroxide ? I use a large amount for variouspurposes and find it expensive to keep con-tinually buying the peroxide." (R. P.,South Wales.)

Many and various are the means of pro-ducing hydrogen peroxide, none of whichis of the slightest use for small scale produc-tion, which is always a costly job. Theusual laboratory method is to allow a diluteacid to react with sodium peroxide, whichis added a little at a time. Hydrogenperoxide is set free and remains dissolvedin the water. A cheap method of buyingperoxide is to obtain it in 100 per cent.concentration. This product is of a syrupynature and extremely dangerous to handleowing to its caustic nature on the humanskin, and also the explosive violence withwhich it liberates oxygen gas if kept in awarm place. For use, of course, thisconcentrate is diluted with water.

Hydrogen peroxide solution is not costlyby any means, and provided that you geton to the right market, assuming that you areusing the quantity you state you will be ableto buy it at a ridiculously cheap figure.There can be no point in home manufactureof such a product which is produced com-mercially by electrolytic means at smallcost.

" INTERESTING FACTS ABOUT RAYS "" With reference to your article on

Interesting Facts about Rays,' I requireinformation regarding the aura seen by theaid of a dicyanin screen.'

" I have obtained the dicyanin solution,but the results have not been quite satis-factory.

" I should be glad if you will kindlyinform me on the following :-

" (1) What is the thickness of the screenwhich gives best results ? and is Vita glassnecessary ?

" (2) What is the action on the eye, orin what way does it render these raysvisible ?

" (3) Does dicyanin transmit ultra -violetrays ? (F. H., Birmingham.)

Yours is a common experience. Manypeople, even after having sensitised theireyes with dicyanin, are unable to see thehuman aura. So much so is this that itis considered in some quarters that suchindividuals are congenitally incapable ofseeing the human aura. This observation,however, has never been proved and, tosay the least. is doubtful.

The thickness of the dicyanin screen isquite immaterial. A vita -glass screen isnot necessary.

The so-called sensitising action of dicyaninon the human retina is quite .unexplainedat the present day. Probably the peculiarblue light coming through a dicyaninscreen may have a slight paralysing effect

e must be enclosed. Every query and drawing which Isbe accompanied by the coupon appearing on page iii ofMECHANICS, Geo. Newnes Ltd., 8-I I Southampton

London, W.C.2.

on the retina, making it less sensitive to therays of white light.

Dicyanin transmits blue rays. But itstransmission is not a " sharp ' one. Thedicyanine of commerce is a mixture ofthree dyes, and it is doubtful whether puredicyanin has ever yet been prepared.Dicyanin's main use was formerly that ofinfra -red sensitiser for photographic plates.It has now, however, been superseded forthis purpose by the more efficient dyes,kryptocyanine and neocyanine, discoveredin 1919 and 1925 respectively. Both thesedyes do not appear to confer " aura -sensitivity " on the human retina.

Truth to tell, the whole subject of thehuman retina is, as yet, in a very unsatis-factory state of explanation. That theaura does exist is an established fact-what it is exactly and how it is best to beseen are, as yet, unknown.

In 1920, a Dr. Frederick Kilner, then anold and retired man living in Southampton,wrote a book which he entitled " TheHuman Aura." This work was publishedby Methuens. It is now out of print, butwould probably be obtainable from a firmof secondhand booksellers, as, for instance,Messrs. Foyles, of Charing Cross Road,London, W.C. 2. Kilner's " Human Aura "is still the only work on this most interestingsubject.

ELECTRICAL QUERIES" (1) How could I calculate the amount of

wire required to make solenoids to work off(a) a car battery, and (b) the electric mains ?Is it necessary to use a resistance to avoidblowing the fuse or damaging the battery ?

" (2) I have been experimenting with anarc -lamp, using the wire from an old electricfire as resistance. I had an idea that ifless wire was used there would be morecurrent to give a bigger arc, but on cuttingthe wire in two I did not notice an improve-ment. Why is this ? Would using morewire give more current at the points ?

" (3) Would it be possible to make anelectric petrol gauge by using an ordinaryvoltmeter, or ammeter, and utilising a coilof resistance wire to alter the reading ? Ifso, what type of wire is needed and howmuch ?

" (4) Referring to the arc -lamp again, Ihave used jars of water to which a littlesalt had been added, as resistances, andthese gave a far larger arc than did theresistance wire from the fire. How is this ?Do the jars cut down the voltage or theamperage of the current ? " (L. R.,Belfast.)

The amount of wire on an electro-magnet depends upon the purpose forwhich the magnet or solenoid is designed,but the power of a magnet depends on theproduct of the ampere and the turns.Thus you can get the same result with oneturn and 10 amperes or 1 ampere and tenturns.


a


If you only desire a small magnet forexperimental purposes, then calculate theamount of wire by its resistance found byexamining the makers' lists.

Quite a moderate arc lamp requires5 amperes, this means that it requires aresistance of 30 ohms in series, the reasonbeing that the arc needs 5 amperes at60 volts, thus a resistance is needed toabsorb the unwanted 150 volts. This isfound by Ohm's Law to be 30 ohms. Youwere probably using a resistance of about100 ohms, but you should have noted abigger arc when removing part of the wire ;a dirty contact probably caused the trouble.We cannot quote the wire needed for thepetrol gauge, as it is essential to know theresistance of the voltmeter. The jarsobviously had a lower resistance and letmore current pass. You have a wrongconception of amps, volts, etc., and youwould profit enormously by reading the twosmall books, " Accumulators " and " SimpleElectrical Apparatus," obtainable fromMessrs. Geo. Newnes Ltd., 8-11Southampton Street, W.C.2, is. 2d. postfree. The first chapter of " Accumu-lators " deals fully with the question ofOhm's Law.MISCELLANEOUS QUERIES

" Could you please inform me on thefollowing :-

" (1) How is paper treated with potassiumiodide for use in electro-chemical tele-graphy ? Are there any other chemicalsolutions which produce the same effect ?(non-poisonous).

" (2) What is Thermit ' (or Thermite ')used for ? What is its composition ? Is itpossible to make it ?

" (3) What is the composition of a goodhectograph and the method of working ?

" If newspaper printing is done withaniline ink, would it be possible to takeimpressions of newsprint on to a hectograph ?

" I have made a quantity of ink by placing' lead ' of a copying ink pencil into boilingwater. Is this a good substitute for anilineink for use with the hectograph ?

" I would be very much obliged if youcould let me have the above information, asI have looked through many magazines andbooks without finding it." (J. B. H.,Telscombe Cliffs.)

(1) Paper is treated with potassium iodidefor electro-chemical use, by soaking it for afew minutes in a 10 to 25 per cent. solutionof potassium iodide, and then by drying it.The exact strength of the potassium iodidesolution is determined by the type of paperused (it should be best white filter paper-not ordinary blotting paper, which is toothick and which absorbs too much of theiodide solution) and, also, the precisecurrent -intensity under which it is intendedto work. Such details, therefore, can onlybe determined by actual trial and experi-ment.

Paper treated with potassium iodidesolution alone will give a yellow or browncolouration when submitted to electro-chemical action. If, however, a few dropsof starch solution are added to the iodidesolution, the subsequent colour developedon the paper will be blue. Be sure, how-ever, that the potassium iodide solution isperfectly neutral before you add the starchsolution, otherwise a blue colouration willappear in the solution itself.

Another chemical solution which developsa colouration on paper under the influenceof electro.chemical action is a 10 to 25per cent. solution of prussiate of potash towhich a few drops of nitric or hydrochloricacid have been added. Prussiate of potashis not a scheduled poison in the strict senseof the term. Nevertheless, it cannot be

said to be non-poisonous. Paper wettedwith this solution gives a blue or brownishcolouration upon contact with the positivepole of a battery or circuit.

(2) The material known commercially as" Thermite " is a mixture in varying pro-portions of aluminium powder with variousmetallic oxides. It is used in the Gold-schmidt or " Aluminothermic " process ofwelding. The thermite is heated eitherelectrically or by means of some pyrophoricmixture, whereupon a very energeticreaction sets in, the aluminium combiningwith the oxygen of the oxide and thusliberating the free metal which effects thenecessary welding.

You could make thermite mixture foryourself by mixing aluminium powder withferric, chromium or similar metallic oxides,but you would find it necessary to heat itto a very high temperature, say bright -redness, before the " thermite reaction "commenced.

(3) A hectograph, as you know, is agelatine pad which is used for duplicatingletters and other writings by the method oftransfer.

Either of the following recipes will pro-vide a good hectograph pad, the first recipebeing the simpler of the two, but wearingmore rapidly :-

(a) Gelatine . . 1 oz.Glycerine . . 6 oz.Sugar . 1 oz.Water . . 4 oz.

(b) Gelatine . . 31 oz.Glycerine . . 31 oz.Sugar . oz.Dextrine . . 1 oz.Zinc oxide . 1 oz.Water . . 21 oz.

If gelatine cannot be obtained for making -up the above formulm, powdered glue maybe substituted.

The gelatine or glue is first soaked andthoroughly dissolved in the water, theremainder of the ingredients being addedsubsequently. The zinc oxide, of course,employed in the second recipe is not solublein water. When all the ingredients havebeen well mixed together, the resultantliquid is poured into a flat tray and left toset. If the setting of the mixture is notsatisfactory, the tray should be heatedgently over a gas ring in order to drive offa little of the water.

To work this hectograph, the writing tobe copied is done in, aniline ink. Yourmethod of dissolving the purple " lead "of copying -pencils in water would beeffective as a substitute for an aniline ink,but it is not likely to give the best results.

A good violet ink for hectograph use ismade as follows :-

Methyl violet crystals 1 partSugar . . 1 part Parts byMethylated spirit . 1 part weightGlycerine . 2 partsWater . . 12 parts ,Mix the methylated spirit with the

glycerine and then dissolve the methylviolet in the resultant mixture. Dissolvethe sugar in the water and then mix thetwo solutions well together. This ink willkeep indefinitely.

Characters varitten with this ink aretransferred to the hectograph pad byallowing the paper on which they arewritten to make firm contact with the padfor a short time. The paper is thenremoved, after which copies can be takenfrom the pad by pressing clean white paperin contact with it.

For success to attend results, a home-made hectograph usually requires a con-siderable number of trials to be made beforethe right working conditions are obtained.

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Newsprint, not being effected in ink ofthe above character, cannot usually besatisfactorily hectographed. A few trials,however, would inform you on this point.

THE INDIAN ROPE TRICKThe following is a reader's solution to the

Indian rope trick published in our Marchissue.

" I rule out the possibility of magic as thesolution to ` The Indian Rope Trick ' whichyou kindly invite readers to solve, and asthe trick is performed in open air, I thinkit is safe to assume that the rope is theonly part that is not genuine. The rope,of course, would have to be rigid whilebeing ascended, and flexible while beingexamined, and to have these properties Isuggest that it could be constructed in thefollowing way :-

" The whole length could be cored withidentical steel bushes about in. long byir in. outside diameter, and -{isin. bore, theends of which, being machined spherical(slightly) to fit each other. One end isconcave and the other convex, and a fin.diameter steel cable is passed through thecentres of the bushes and attached firmlyto the ' top ' end bush. The other end ofthe cable (the base end) would be providedwith a tensioning arrangement which couldbe a nut and screw. The nut being in theform of a twist grip to represent the bindingat the end of the rope.

" For realistic appearance, the ropewould be braided, and this would alsoserve to position the bushes.

" To make the rope rigid, the steel cablewould be highly tensed, which would com-press and lock the bushes together inwhatever position they happened to be.By slightly tensing the inner cable, therope would be partially stiff, enabling itto be ' erected.' With the inner cablerelaxed, the rope would seem quite naturalwhen examined. These operations would,of course, have to be done surreptitiouslyduring the ' ritual.' " (E. B., Staffs.)

A MAINS UNIT FOR 9.5 MM. CINEMASIn the article on page 287 of the March

number of PRACTICAL MECHANICS adraughtsman's error occurred in the pic-torial circuit and in the wording on thelayout plan.

A " mains socket " is indicated on theplan, and this should read " mains plug."Actually the socket is connected to themains lead. In the pictorial circuit a" mains plug " should be substituted forthe " A.C. mains socket " shown ; thereforeconstructors should substitute accordinglya suitable plug and socket, namely, theBulgin type P.O.g

FACTS ABOUT BENZOLE

DURING the war benzole was used as asubstitute for petrol when our supplieswere failing. If everyone can become

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Every now and then we hear scare state-ments on " our coal reserves are failing."How untrue and exaggerated those are canbe judged by the fact revealed not long agoby Sir Frank Smith, of the Department ofScientific and Industrial Research, that evenat our present colossal rate of consumptionthere are reserves in British coal fieldssufficient for nearly 500 years.

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PRACTICAL MECHANICS"


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Complete range of CHEMICALS in Bottles from 3d. each.-Extensive selection of APPARATUS, including Beakers,Flasks, Graduated Ware Condensers, Retorts, Balances, etc.SPECIAL PARCEL OF APPARATUS.1 Flask, flat bottom 150 c.c., 1 Beaker, spouted 100 ac., 3 TestTubes 4 in. x 4 in., 1 Thistle Funnel 20 cm., 3 ft. f

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21, I ins. in 6 mths. micas- No20, 31 ins. in 16 d'ys. Drugs. No30, 2 ins. in 4 wks. Dieting.40, 11 ins. in 6 wks.

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CINEMATOGRAPH FILMS.-Standard size from6d. 100 feet. Machines, Accessories. Sample Films,1/- and 2/6 post free. Catalogues free.-" Filmcries,"57 Lancaster Road, Leytonstone, E.11.ELECTRIC CLOCKS-MOVEMENTS-PARTS.

Mechanical clocks CONVERTED toSYNCHRONOUS OR IMPULSE .. 30/ -SELF WINDING (Mains or Battery) .. 36/-MASTER CLOCKS .. .. From £10/1010Small Machining and Instrument Work-PatentModels built.-Tho F.B.M. Gear Syndicate Ltd.,45149 Brighton Road, S. Croydon.

" SUCCESS" MOULDS make Solid and HollowToys, etc. List Free.-LEE'S, BENTINCK ROAD,NOTTINGHAM.

REAL PHOTOGRAPHS. Railways, Aeroplanes,Ships. Send 3d. for Specimen Card and List of anySection.-Real Photographs Co., 9 Union Court,Liverpool 2.

SPARE -TIME SALESMAN wanted. Experienceunnecessary. 20/- weekly easily earned.-Apply"Salesman," Richfords Ltd., Snow Hill, London.

NEW 3 -INCH Precision, Toolroom, Back Geared,Screw Cutting Lathes. £6/7/6. Photo. Stamp.-John P. Steel, Bingley,

SUPER A.C. MOTORS. All sizes at bargainprice's.-A. Musham, Killinghall Road, Bradford.

INVENTORS' and ENGINEERS' Drawings,Models, Patterns.-Bland, 105a Crawford Street,London, W.I.

HAVE A DETAILED DRAWING of your petidea. Mail me rough sketch for free estimate.-Carder,15 Wolseley Road, London, W.4.

MOVIES AT HOMEHo7 to make your own CinemaP rojector. Particulars free.

Moviescope (N), 116 Brecknock Road, London.

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This coupon is available until May 31st,1935, and must be attached to all letters con-

taining queries.PRACTICAL MECHANICS, MAY, 1935

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tie etasClub Reports for inclusion tel this feature should notexceed 250 words in length, and should be received notlater than the 12th of each month for inclusion in thesubsequent month's issue.

STREATHAM COMMON MODEL RAILWAY CLUB,WE have had two very interesting lectures this last

month, one by Mr. Brightman of the West EssexClub on " Building of 00 ' Gauge Models in Brass andWood," in which he described his own models-somevery nice coaches, wagons and a loco ; and one by Mr.Taylor (member) on "High Capacity Wagons."

We cordially invite you to our clubroom at 201Gleneldon Mews, High Road, Streatham, S.W.16, onany Friday.

We have lust made the positions of President andVice -Presidents and they have been filled by W. B.Hart, Esq., M.I. Loco E., as President, and Messrs.J. N. Maskeleyne, A.I. Loco E. and C. H. Stephens.

The Fourth Annual Exhibition is being held on June7th (6.30 p.m. -9.30 p.m.) and June 8th (2.30 p.m. -9.30p.m.) at the Waterworks, 70 Conyers Road, Streatham,S.W.16, to which we invite all readers. Tickets, price6d. each (for both days), as well as full particulars ofthe club, can be obtained from the Secretary, BrookeHouse, Rotherhill Avenue, Streatham, S.W.16.

INSTITUTE OF SCIENTIFIC RESEARCHON Friday, March 29th, a visit was paid to the

Distributing and Maintenance Dept. of Leeds GasWorks. After seeing the Plumbing Dept., we wereshown how old gas stoves and gas fires are cleaned,mended, and renovated, and concluded this interestingvisit by seeing the various parts of gas meters beingmended and tested.

On Saturday, March 18th, a meeting of the LeedsRadio Section was held, and on Saturday, March 23rd,a meeting of the Leeds Physics and Chemical Sectionwas held. On Wednesday, April 24th, we paid a visitto Kirkstall Power Station, Leeds.

We are now conducting a " more members " cam-paign, and are also endeavouring to form new branches.We shall therefore be pleased to hear from anyone whowould be willing to form a branch, and also from anyprospective member.

Readers in Leeds should communicate with F.Underwood, 11 Sandhurst Grove, Leeds 8; readersin Canterbury with J. H. Potts, 16 Whitstable Road,Canterbury ; and all other interested readers withD. W. F. Mayer, 20 Rollin Park Road, Leeds 8.

MAKING A - THERMOPILE(Continued from page 351.)

produced when a finger is placed on thejunctions. A case for the instrument ismade from -1-in. plywood in the form of along box about 4 in. by 1 in. square. Agroup of elements are mounted in one endso that they are flush with the opening,and terminals are fixed to the box. Thesecuring of the unit in the box is mosteasily done by using the assembling bolts,which should be made a little longer for thepurpose. The box should be made with thelid left off and secured to the stand. Theelement is now mounted by passing thebolts through holes in the wood, and the lidis then fixed in place. A hinged lid, also ofwood, is fixed to the element end of the boxso that it can be closed down to shut offunwanted radiations, and also to protect theinstrument when not in use. A similar lidcan be fitted to the other end. The reasonfor making the long box is to protect thecooled junction from draughts and keep thetemperature constant when in use. A standcan be made from a base of hard wood about3 in. square to the centre of which a roundupright is fixed, and the box is mounted onthe top of this (see Fig. 5).

To. the reader who, has had little experi-ence with thermopiles and thermo-electricitythe above may still leave him in the dark,but the article is intended for those whohave experimented slightly and understandthe principles. .

1,1)SSC(oGOOD IDEAS-

are often rejected because of uncon-vincing drawingsLet us prepare attractive illust,ationswhich will convey your idea quickly andclearly to Manufacturers, Editors.Agents, etc.We specialise in Patent Oilice and Tech. -

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INSTALLING DOMESTIC ELECTRICAL DEVICES

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Transcript of INSTALLING DOMESTIC ELECTRICAL DEVICES