J O U R N A L O F

Architectural Conservation

Consultant Editors:

Professor Vincent Shacklock

Elizabeth Hirst

Professor Norman R. Weiss

Bob Kindred MBE

Professor Peter Swallow

Number 3

Volume 16

November 2010

Copyright © 2010 Donhead Publishing Ltd

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means electronic, mechanical or otherwise without prior permission from the publisher, Donhead Publishing.

Donhead Publishing Lower Coombe Donhead St Mary Shaftesbury Dorset SP7 9LY Tel: 01747 828422 www.donhead.com

ISSN 1355-6207

Cover photograph: Stowe House, Buckinghamshire, wrought iron lantern over central Marble Saloon. Courtesy of Ed Morton, the Morton Partnership Ltd. Background image was commissioned by Selby Abbey for repair work undertaken by Purcell Miller Tritton.

Typeset by Bookcraft Ltd, Stroud, Gloucestershire Printed in Great Britain by TJ International Ltd, Padstow

Journal of Architectural Conservation November 2010

Tuff Stone Masonry near Tower Hill in Victoria: Fragmentary Remains of Pioneer Settlement in Australia

Chris How, Marie Jackson, Catherine Woolfitt

Abstract

Examples of volcanic tuff in pioneer buildings have been identified in western Victoria, Australia, in the vicinity of the Tower Hill volcanic cra-ter. A field study has highlighted the use of tuff (notably in small domestic buildings dating to the early years of the colony) and has prompted inves-tigation of these fragmentary and often neglected remains, including as-sessment of their present condition. The study and petrography of the vol-canic tuffs from several cottages and a church, coupled with observations of the building stones by James Bonwick made in 1857, provide further insights into the durability and weathering characteristics of the local tuff stones. These stones are comparable to those used extensively in ancient Rome, as described by Vitruvius, who provided guidance on their physical properties and use. Recent re-assessment of the deterioration of these tuff stones has shown just how relevant that advice remains today.

Historical context

During the mid 1830s the open secret of suitable agricultural land on the mainland led to a rather tenuous settlement of south-eastern Australia from Launceston in Van Diemen’s Land (Tasmania). The dearth of arable land prompted a few pioneer families to risk illegal farming on locations across Bass Strait that had hitherto seen only sealing or whaling parties. Two safe anchorages were available on the mainland at Portland Bay and the river mouth at Port Fairy, but the occupation soon spread along the coast to a less secure anchorage at Warrnambool (Figure 1). The better known early settlements at Melbourne and Geelong developed concurrently (also from

92 Chris How, Marie Jackson, Catherine Woolfitt

Van Diemen’s Land) and independently of the Western District, which for some time had little contact with either Port Phillip Bay or far away Sydney.

‘Volcanic Region’

In April 1836 Major Thomas Mitchell, an experienced explorer and Penin-sular War veteran, left Sydney to probe south-westwards into unknown country. After a journey of five months, he was surprised to encounter the embryonic settlement at Portland Bay; this marked the first official aware-ness of a European presence on the mainland south coast. His journey had led him across what he described as ‘Australia Felix’, land suitable for grazing and other farming.1 A later traveller described it as the ‘Volcanic Region of Australia’.2

The remoteness of the location forced the early settlers to turn to building materials at hand, which included basalt lava flows at Portland Bay and Port Fairy, and the dune limestone at Warrnambool. The volcanic crater of Tower Hill nearby had erupted volcanic ash over a significant part of the surrounding area, some of which formed lithified volcanic ash or ‘tuff’ (i.e. ash transformed into stone). The tuff could be easily extracted and worked, but varied in texture and durability. The better lithified deposits occurred in valleys and soft tuff from the Merri Valley (Figure 2, Quarry 3) was selectively used in the early years of settlement as quoins and other dressings in Christ Church, Warrnambool (Figure 3; see also Figure 7), and

Figure 1 The seaward settlements of Victoria’s south coast.

Tuff Stone Masonry near Tower Hill in Victoria 93

Figure 2 Map of the Tower Hill volcanic crater with cottage locations and quarry sites.

in three churches in Port Fairy. Its later use (up to 1900) was confined to firebacks in cottages and houses (see Figure 4).

Tower Hill is a prominent landmark and is significant for a number of reasons, including its geology and its importance for Aboriginal people and their predecessors whose artefacts, axe heads and flakes have been uncovered in the area. The natural environment of Tower Hill suffered damage, loss of flora and fauna as a result of European settlement and the fragmentary building remains described below3 are associated with this period of history.

Tower Hill was declared Victoria’s first national park in 1892 in an attempt to halt the environmental damage caused by the activities of European settlers (land clearance, grazing, crops and quarrying). James Bonwick, an inspector of schools who toured the area in 1857, had noted the natural environment, commenting on the beauty of its gigantic ferns and other vegetation, and made a plea that it be preserved for posterity. The area has been protected as the Tower Hill State Game Reserve since 1961 and is on the Victorian Heritage Register. Various native plants and animals have gradually been reintroduced.

Geological setting of the Tower Hill tuff building stones

Tower Hill volcano is a young, well-preserved volcanic cone or maar produced by a series of shallow, explosive eruptions beginning about 35,000 years ago.4 Accumulations of coarse and fine volcanic ash, tuff and other extruded material form its rim, containing a crater lake. Deposits of

94 Chris How, Marie Jackson, Catherine Woolfitt

Figure 3 Christ Church, Warrnambool, north side and east end (top). West end tuff lancets of the church in scored dune limestone (bottom).

ash and tuff occur up to 20 km away from the crater (Figure 2). Explo-sive eruptions at Tower Hill occurred when molten rock (magma) came into contact with water-saturated sediments producing clouds of steam, hot gases and tephra (fragments ejected during the eruption including ash, crystals and underlying bedrock from conduits off the eruptive vent).5 In some localities the ash consolidated to form tuff.6 The tephra of the Tower Hill tuff is bound together by natural minerals or cements that give varying degrees of lithification to the tuff building stones.

The dispersive cloud of a pyroclastic eruption may deposit tephra in two ways.

• Airfall deposits accumulate when wind sweeps ash across the coun-tryside as a blanket. At Tower Hill, these form well-defined layers that become thinner and finer grained away from the main crater.7 These airfall deposits are thickest in the north-west, where carried by prevailing winds. The tuff building stones of the cottages north-west of the crater (Figure 2, Quarries 1 and 4) formed from airborne deposits and have a massive, relatively poorly consolidated, fine-grained fabric.8

• Pyroclastic surge deposits form when a vertical eruption column collapses and condensed steam becomes thoroughly mixed with tephra. Turbulent clouds of wet tephra surge away from the vent at high speeds, often carving channels into previously erupted deposits. At Tower Hill these surge deposits form a veneer over the previous topography, thick-ening in older depressions.9 The Merri River surge deposits formed in this way: they are moderately to well-cemented with a more coarse-grained, bedded fabric (Figure 2, Quarries 2 and 3).10

Pioneer volcanic tuff construction

Following an educational tour in 1857, James Bonwick produced an invaluable record of geological and other observations of the landscape.11 A keen observer and an amateur geologist, he noted many cases where volcanic tuff had been used in construction. One particular reference to a building some 40 km north of Warrnambool illustrates the failings of the tuff building stone which are still valid today:

The Mount Shadwell Hotel, an ancient Bush Inn, has a forlorn appear-ance, especially from the dilapidated condition of its walls. These are the tufa [tuff] or ash, but the slabs have been set up edge-ways, and the weather acting upon so porous a material is gradually flaking it away. My friend Dr Curdie uses it horizontally. His chimneys are of slabs with a hole cut through the middle for the smoke.12

Tuff Stone Masonry near Tower Hill in Victoria 95

96 Chris How, Marie Jackson, Catherine Woolfitt

Bonwick’s first impressions of limestone masonry at Warrnambool were favourable. He also described a durable variety of the Tower Hill volcanic tuff quarried along the Merri River (Figure 2, Quarry 3):

The limestone makes an admirable building material, though the use of the Merri stone or tufa [volcanic tuff] for quoins, etc., produces a capital effect. The Merri stone is so called from the indurated kind of ash being found near the Merri river, and which is regularly quarried out. It is superior to any other volcanic tufa. Though brittle to the touch, it is well suited to stand weather, retaining its sharp outline. When pieces of cinder fall out in the process of working, the mason fills up the holes with sand and clay. The stone is thoroughly fireproof; in the late fire of the store of Bateman & Co., the front wall was found wholly uninjured. It is employed in the construc-tion of the arches of ovens, for which it is more valued than firebricks. Workmen do not favour it so much, on account of the injury done to their tools by the siliceous cindery grit, though the stone is easily worked.13

Bonwick gives a perceptive summary of the physical characteristics of the Merri Valley tuff masonry. The building stones are relatively well consolidated, durable and resistant to weathering. They are superbly fire-proof and easily worked into dimension stone and firebacks. The ‘cindery grit’ that dulled tools and cutting edges are sand-sized fragments of lava and crystals.14 Bonwick accurately notes that the tuff is brittle and will weather badly if its bedding plane is laid vertically.

Figure4 Volcanic tuff fireback of a former lean-to kitchen surrounded by an 1850 Pleistocene dune limestone external wall (chimney excised).

The fireproof qualities recorded by Bonwick are borne out by a number of extant firebacks (Figure 4) found across the district, which are invari-ably set with the strata laid vertically. These are typically 900 mm wide by 600 mm high, and 150–200 mm thick. They are often exposed on the external walls of buildings and consequently suffer external delamination.

Bonwick made one further significant observation of direct interest when he departed from Warrnambool for Tower Hill to inspect the crater and associated deposits: ‘The ash, tufa, or tuff of Tower Hill is not of the solidity of that of the Merri. Spread over the road it makes a capital covering, but it is too soft for building.’15

Cottages and churches constructed of Tower Hill volcanic tuff

Inspection of the Tower Hill tuffs used in pioneer buildings close to the crater confirms Bonwick’s observations: the tuff deposits from which stone was quarried were poorly consolidated or lithified. Tuff was used for a dwarf plinth to a diminutive weatherboard cottage that sits high on the tuff ring of the crater and is known locally as Granny Malady’s Cottage (Figure 2). The cottage measures only 2.7 m by 4.3 m on plan, and its namesake was born at the site in December 1851 before the cottage was completed. The plinth stonemasonry, although weak and fragile, sits on a bed of loose airfall deposit, high and dry on the crater rim.

Eagan’s Cottage, Crossley

A semi-ruined farm shed constructed from tuff was found about 2 km to the west of the crater rim, sited alongside a stream (Figure 2). Closer examination found this to be a small former residence. Stylistic features, linings and nails indicate that the dwelling was built in the late 1890s. The structure is in a dilapidated condition and the tuff stone has weathered poorly. The masonry had been cut with some care by an experienced hand, the quality of work being evident particularly in the formation of door and window openings. The tuff stone was extracted from an area alongside a stream near the cottage (Figure 2, Quarry 1); it is soft and poorly cemented, with abundant fine, glassy ash weathering to clay. The condition of the cottage’s plinth is very poor since the plinth layer is very close to the winter water table, is porous and composed of inferior, high clay content tuff; the decay is evident in Figure 5c.

The condition of the structure is now precarious due to a combination of factors:

• severe weathering and erosion of the masonry at the foot of the walls;• disuse;• lack of proper repair and maintenance.

Tuff Stone Masonry near Tower Hill in Victoria 97

98 Chris How, Marie Jackson, Catherine Woolfitt

Figure 5 Eagan’s Cottage, Crossley: (a) North end elevation; (b) South-east corner internal view, with window crudely infilled with sandstone; (c) Decay of chimney plinth stones at north end; and (d) Outward bow and core collapse west side, rebuilt with dune limestone.

However, the weathering of the chimney base of Eagan’s Cottage (Figure 5c) exceeded decay that might typically be associated with capil-lary moisture rise and these stones appeared, and felt, noticeably soft and friable. Possible explanations for this severe deterioration included:

• the vulnerability of tuff stone to saturation (a characteristic of tuff stone, in general, which has been identified by others and is discussed further below);

• open joints which contribute to damp; • variations in the original volcanic tephra compositions and subsequent

lithification of the tuffs (which might account for the striking variation in their durability).

(a) (c)

(b) (d)

Loss of sections of original masonry and unsympathetic repair work in limestone have further exacerbated the situation to the extent that this humble structure is beyond the point of intervention using good masonry repair work. Substantial stone replacement and reconstruction and other structural repairs would now be necessary and these are not feasible for various reasons including a lack of resources. In these circumstances, recording and dissemination of information about the building are the principal measures to mitigate further loss of the building fabric.

Sheehan’s Cottage, Crossley

About 3 km to the west of the crater rim (Figure 2, Quarry 4), the tuff chimney at Sheehan’s Cottage appears quite similar to that at Eagan’s Cottage, but the tuff is finer grained with more weathering to clay. The tuff chimney was the only masonry element in this weatherboard cottage and was rendered over until exposed during demolition. Many similar chim-neys exist in the nearby township of Koroit.

The tuffs from both Eagan’s and Sheehan’s Cottages have a coarse texture and appear less durable than the tuffs quarried along the Merri River (Figure 2, Quarries 2 and 3) which were used to good effect in quoins and buttresses in Christ Church, Warrnambool (Figure 3). There is little evidence of the cinder particles visible at Christ Church and described by Bonwick.16 Both cottages are sited on a flat flood plain vulnerable to damp ground conditions. It is hardly surprising that at Eagan’s cottage the tuff masonry at the base of the chimney was collapsing to a powdery mass. As discussed below, the tuffs are particularly vulnerable when saturated with water. Similar decay at the foot of the wall on the weathering side had led to outward rotation, progressive collapse of the core fragments and total collapse of a long section of unsupported masonry. There was widespread evidence of pinch spalling of stonework on corners, door and window openings relating to loss of mortar in the joints. Had the building remained in use, appropriate remedial work (including repointing, deep tamping of joints and selective replacement of heavily deteriorated stones at the foot of walls) could have prevented the development of serious masonry defects.

Kelson’s Cottage, Station Street, Dennington

In contrast to these examples, there is a tuff cottage, located some 11 km away and close to Warrnambool, which has survived with little evident deterioration. This can be dated with some accuracy to between 1856 and 1858, predating Eagan’s Cottage by about 50 years. Situated in an equally exposed location, its comparatively sound state of masonry preservation was surprising. Kelson’s Cottage stands on an elevated point on the Merri River about 4 m above river level. The whole of the river valley suffered

Tuff Stone Masonry near Tower Hill in Victoria 99

100 Chris How, Marie Jackson, Catherine Woolfitt

Figure 6 Kelson’s Cottage, Dennington: South elevation with little change bar the extended chimney (top). North elevation with no obvious deterioration (bottom).

unprecedented flooding in 1946, but this was probably the only occasion when the building got ‘wet feet’. In terms of exposure, there is little differ-ence between Eagan’s and Kelson’s Cottages as both sites are open to the west. Kelson’s Cottage is slightly more exposed, close to the river bank and with a side wall facing directly into the prevailing winds. Site inspections revealed that the building stone was quarried from a nearby exposed bluff of well-cemented tuff (Figure 2, Quarry 2). While the Crossley tuff is an even light grey colour, the Dennington stone contains many sand- to gravel-sized cinders in a more compact, medium grey matrix as described by Bonwick.17 In this respect it is very similar to the quoins and plinth stones at Christ Church in Warrnambool and St John’s Church in Port Fairy.

The quoin stones and lintels of Kelson’s Cottage retain sharp arrises and sound surfaces with only minor friability visible on the lower courses. The lime mortar has suffered little degradation and the sound state of the masonry is in remarkable contrast to that of Eagan’s Cottage. Kelson’s Cottage was occupied until the 1990s and is in an adequate state of repair; the roof is still watertight and corrugated iron sheet has been laid over the original Messmate shingles providing, in effect, a double roof. The marked contrast between the cottages can be partly explained by the different ground conditions and partly by the continuity of use of Kelson’s Cottage. The footings of Kelson’s Cottage sit directly on a firm, permeable tuff bedrock of excellent bearing capacity. Isolation too plays a part, as the cottage is located some 230 m off the nearest road in fenced off farmland, free from vandalism and robbing for material. It was occupied until eighteen years ago, which has benefits for the preservation of both masonry and timber. Abutting structures also have afforded a degree of protection.

Christ Church, Warrnambool

Bonwick visited this newly built church in 1857, a year after the comple-tion of the south nave, and was impressed with the sculptured Merri ash ‘supplied for quoins and grotesque figure heads and other ornaments, which are admirably sculptured’. As Bonwick noted, the church was built of lime-stone (dune limestone) quarried from about 400 m north of the church. The plinths, quoins, window reveals and copings were of Merri stone (tuff), quar-ried in the Merri River valley. Quoins and plinths in the older south section are more uniform in colour and composition, and have weathered better than in the later north nave. Closer inspection of the north quoins reveals a more porous and cindery quality to the stone. In contrast, the south-west corner plinths are moderately well cemented tuffaceous sandstone, the stone identification being confirmed by petrographic analysis. In this case the rate of deterioration appears to relate directly to the stone type and composition.

Tuff Stone Masonry near Tower Hill in Victoria 101

102 Chris How, Marie Jackson, Catherine Woolfitt

Some comparisons with ancient Roman masonry

Recent studies of the composition and physical properties of tuff building stones used in the Roman period are instructive in the context of the Tower Hill tuffs. These studies have reassessed the observations of the Roman architect Vitruvius concerning the nature of tuff stones and have analysed tuffs quarried by the Romans to determine their physical properties and weathering characteristics.18,19

Vitruvius in the late first century bce20 gave highly accurate empirical descriptions of the material characteristics of the Lapis Albanus, Tufo Giallo della Via Tiberina and Tufo Lionato tuffs which are supported by geotechnical analyses.21,22 He recommended that these ‘soft and yielding stones’ be placed under cover or protected with plaster so that they do not ‘crumble apart and dissolve’. Vitruvius also described the fire-resistant characteristics of the Roman tuffs.23 The porous, weakly cemented textures of these tuffs (and the Tower Hill tuffs) readily accommodate expansions during heating, so that they have relatively low thermal linear expansions at urban fire temperatures.24 Pioneers

Figure 7 (a) North-west corner protected side of church, with 1861 plinth decay. The plinth is composed of Tower Hill volcanic tuff (sample CHRCHURCH-01 in Table 1) with a significant percentage of lava and crystal fragments. (b) South-west corner of church. The south-facing 1856 plinth composed of tuffaceous sandstone (sample CHRCHURCH-02 in Table 1) is in good condition.

specifically selected volcanic tuff firebacks for these same reasons (Figure 4). Limestone, on the other hand, undergoes a strong thermal linear expansion and chemical alteration causing the rock to fracture at higher temperatures (as Vitruvius described). Various authors have noted the high porosity of tuff and associated vulnerability to water saturation.25, 26, 27 Porous tuffs absorb large quantities of water, in the region of 15–20% of their weight, and when saturated their compres-sive strength is reduced by as much as 50%.

Vitruvius advised that tuff stones should be quarried in summer and exposed to the weather for two years before use. Those that survive weathering without signs of decay should then be used for building above ground; any stones that suffer decay should be used below ground in foun-dations only.28 Vitruvius identified the superior characteristics of the well-known volcanic Peperino di Viterbo. This is a glassy welded tuff which is more solid and compact than the tuffs in the vicinity of Rome. Welded tuffs subject to heat and compaction are, in general, more durable and less porous than tuffs formed by airborne deposits without heat and compac-tion under successive layers of tephra.

Examination of the Tower Hill tuff building stones

An understanding of the geology of tuff building stones can assist in the condition assessment of masonry. Variation in the composition and geology of building stones is a factor which needs to be considered in the diagnosis of tuff stone deterioration. The photomicrographs shown in Figures 8 and 9 illustrate some of the conditions found in the buildings described in this article. Details of the samples collected for the study are summarized in Table 1.

Conservation challenges and conclusions

A technical understanding of the Tower Hill tuff stones used in pioneer buildings is only one aspect of the conservation of these modest struc-tures. This must be coupled with an appreciation of the local site condi-tions and a wider view of their significance as remnants of a period in history, the European settlement of Victoria in the nineteenth century, which in this particular case carries associations with unfettered exploi-tation and destruction of a natural environment. It is particularly chal-lenging to make the case for conservation of the built heritage in this context, when the preservation of the natural environment equally makes claims on limited resources for conservation. However, practical and effective masonry conservation measures are not necessarily exces-sively costly.

Tuff Stone Masonry near Tower Hill in Victoria 103

104 Chris How, Marie Jackson, Catherine Woolfitt

An understanding of the tuff stone decay and appreciation of the site conditions is fundamental. The vulnerability of weak tuff stones to saturation needs to be recognized and particular attention paid to damp problems, including rising damp (capillary rise) and potential sources of rainwater ingress such as open joints and fractures. Ensuring basic

Figure 8 Photomicrographs of the Tower Hill tuff building stones: (a) Eagan’s Cottage vitric tuff. Accretionary lapilli (outlined in white) with coatings of very fine vitric volcanic ash altered to poorly crystalline clay mineral (halloysite) are very weakly bonded to a poorly lithified, altered fine vitric ash matrix; (b) Kelson’s Cottage vitric–lithic tuff. Glass fragments (outlined in black) and fewer lava rock fragments (outlined in white) form a weakly grain supported network in relatively well consolidated vitric ash; and (c) Christ Church vitric–lithic tuff. Lava rock fragments (outlined in black) and glass fragments form a fairly well-supported and well-lithified grain network. See Table 1 for petrographic descriptions.

maintenance of building elements that protect masonry from weather (roofs, pointing mortar) is critical for tuff stone. Maintaining free drainage at the foot of walls, clear of invasive vegetation is also important. Hard and impermeable floor or paving at the base of walls would be particularly difficult for tuff stone. A high groundwater table, which is unfortunately present in the case of Sheehan’s Cottage, is also problematic.

Remedial conservation work that might be required, depending on the type and extent of masonry defects, ranges from grouting fractures to repointing and deep-tamping weathered or eroded joints, and localized replacement of very heavily eroded stones. Lime-based materials for this work need to be designed to be physically compatible with the tuff stone. They should be sufficiently durable for external weathering and have the porosity and capacity to absorb water to the same degree as the tuff stone. A hard and impermeable mortar is certain to promote tuff stone dete-rioration. There is potential for the use of volcanic ash in repair mortars, as both an aggregate and a pozzolanic additive, which has yet to be explored. Ash blended with locally available lime putty should produce porous mortars compatible with tuff masonry, subject to careful selection of the ash based on its grade (particle size) and other characteristics. The Romans exploited volcanic ash deposits for the production of lime mortars, a practice described by Vitruvius.

Humble vernacular buildings are among the most endangered; they are typi-cally overlooked or undervalued relative to the more sophisticated, formal and decorative buildings whose historic and artistic significance is obvious. Peter

Tuff Stone Masonry near Tower Hill in Victoria 105

Figure 9 Photomicrograph of tuffaceous sandstone composed of volcanic glass fragments, fossils, and calcite and quartz sand grains, from the south-west corner plinth of Christ Church, Warrnambool.

106 Chris How, Marie Jackson, Catherine Woolfitt

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eral

l. St

rong

wea

ther

ing

to

clay

: 40%

ove

rall.

Tuff Stone Masonry near Tower Hill in Victoria 107Sa

mpl

eL

ocat

ion

Stru

ctur

eM

acro

scop

ic D

escr

ipti

onPe

trog

raph

ic O

bser

vati

ons

KE

LSO

N-0

1D

enni

ngto

nK

elso

n C

otta

ge:

S w

all,

1 m

abo

ve

grou

nd le

vel

Gra

in s

uppo

rted

, fai

rly

wel

l-ce

men

ted,

dar

k ye

llow

ish

brow

n 10

YR

4/2

, poo

rly

sort

ed t

uff,

wit

h co

arse

ash

-siz

ed g

lass

y te

phra

w

eath

ered

to

opaq

ue c

lay

min

eral

. Py

rocl

asti

c su

rge

depo

sit?

Sand

-siz

ed a

lter

ed g

lass

fr

agm

ents

(pa

lago

nite

) fo

rm

~45%

of

vitr

ic0.

49 li

thic

0.17

cr

ysta

l 0.12

tuf

f. L

ava

frag

men

ts:

~14%

. Cal

cite

and

cla

y ce

men

ts:

~21%

. Muc

h di

ssol

utio

n of

gla

ss

and

plag

iocl

ase

Wea

ther

ing

to

clay

: ~35

% o

vera

ll.

KE

LSO

N-0

2D

enni

ngto

nK

elso

n C

otta

ge:

N f

ace;

plin

th

leve

l, 10

in a

bove

gr

ound

leve

l

CH

RC

HU

RC

H-0

1W

arrn

ambo

olC

hris

t C

hurc

h:

NW

cor

ner-

plin

thM

ore

stro

ngly

gra

in s

uppo

rted

, fa

irly

wel

l-ce

men

ted,

dus

ky

yello

wis

h br

own

10Y

R 3

/2, p

oorl

y so

rted

tuf

f. H

as 0

.5–2

cm

thi

ck

laye

rs o

f co

arse

r lit

hic-

crys

tal

teph

ra a

lter

nati

ng w

ith

fine

vitr

ic

teph

ra a

lter

ed t

o cl

ay m

iner

al.

Pyro

clas

tic

surg

e de

posi

t

Sand

-siz

ed a

lter

ed g

lass

fr

agm

ents

(pa

lago

nite

) fo

rm

~40%

of

vitr

ic0.

40 li

thic

0.21

cr

ysta

l 0.12

tuf

f. L

ava

frag

men

ts:

~14%

, qua

rtz

sand

s: ~

3%.

Cal

cite

(an

d cl

ay)

cem

ents

: ~2

4%. M

uch

diss

olut

ion

of g

lass

an

d pl

agio

clas

e. L

ess

wea

ther

ing

to c

lay:

~24

% o

vera

ll.

CH

RC

HU

RC

H-0

2W

arrn

ambo

olC

hris

t C

hurc

h:

SW p

linth

Foss

ilife

rous

, lig

ht o

live

gray

5Y

6/1

, tuf

face

ous

calc

aren

ite

sand

ston

e. S

and-

size

d gr

ains

ten

d to

dis

aggr

egat

e fr

om fi

ne a

sh-s

ized

op

aque

mat

rix.

Lea

ves

a po

wde

ry

resi

due

whe

n ru

bbed

. Rew

orke

d te

phra

and

san

dsto

ne d

epos

it.

Vit

ric 0.

28 li

thic

0.18

cry

stal

0.8

tuff

aceo

us s

ands

tone

. Lim

esto

ne

sand

s (~

11%

), qu

artz

san

ds

(~7%

), pl

agio

clas

e (~

8%),

clay

pe

loid

s (~

6%)

and

mac

rofo

ssils

(<

2%)

are

cem

ente

d by

fine

, re

wor

ked,

alt

ered

vit

ric

teph

ra

and

calc

ite

(23%

).

A.G

.L. =

abo

ve g

roun

d le

vel.

Tab

le 1

C

ha

rt o

f sa

mp

les

co

llec

ted

an

d h

an

d s

am

ple

de

scri

pti

on

s.

Sam

ple

Loc

atio

nSt

ruct

ure

Mac

rosc

opic

Des

crip

tion

Petr

ogra

phic

Obs

erva

tion

s

EA

GA

N-0

1Sc

otts

Roa

d,

Cro

ssle

yE

agan

’s C

otta

ge:

Chi

mne

y 2’

A

.G.L

.

Wea

kly

grai

n su

ppor

ted,

m

oder

atel

y w

ell-

cem

ente

d, p

ale

yello

wis

h br

own

10Y

R 6

/2, p

oorl

y so

rted

vit

ric

tuff

. Fin

e vi

tric

tep

hra

alte

red

to c

lay

min

eral

. Cal

care

ous

efflo

resc

ence

may

per

vade

alt

ered

vi

tric

mat

rix.

Pyr

ocla

stic

sur

ge

depo

sit.

Poro

us, a

lter

ed v

itri

c m

atri

x fo

rms

35–4

0% o

f vi

tric

0.39

lit

hic 0.

16 c

ryst

al0.

9 tu

ff.

Acc

reti

onar

y la

pilli

com

mon

. L

ava

frag

men

ts: ~

10%

. Wea

k ca

lcit

e ce

men

ts: ~

35%

ove

rall.

W

eath

erin

g to

cla

y: ~

30%

ov

eral

l. Pl

agio

clas

e co

mm

only

al

tere

d to

cal

cite

.

EA

GA

N-0

2Sc

otts

Roa

d,

Cro

ssle

yE

agan

’s C

otta

ge:

Mos

sy, w

eath

ered

w

est

wal

l

EA

GA

N-0

3Sc

otts

Roa

d,

Cro

ssle

yEa

gan’

s C

otta

ge:

Insi

de fa

ce, S

W

Cor

ner,

3’6’

’ A.G

.L.

SHE

EH

AN

-01

Shee

hans

R

oad,

C

ross

ley

Cot

tage

chi

mne

y,

4’ A

.G.L

.W

eakl

y gr

ain

supp

orte

d,

mod

erat

ely

wel

l-ce

men

ted

vitr

ic

tuff

sim

ilar

to E

AG

AN

-03.

Ver

y si

mila

r to

Eag

an C

otta

ge,

but

mor

e fin

ely

grai

ned

wit

h m

ore

wea

ther

ing

to c

lay.

TO

WH

ILL

-05

Tow

er H

ill

crat

er, N

sid

eB

elfa

st q

uarr

y (?

)Po

orly

gra

in s

uppo

rted

, mod

erat

ely

wel

l-cem

ente

d, p

ale

yello

wis

h br

own

10Y

R 7

/2 fi

ne-g

rain

ed, l

apill

i tuf

f. Fi

ne a

sh-s

ized

vitr

ic te

phra

alte

red

to c

lay

min

eral

. Lea

ves

a po

wde

ry

opaq

ue r

esid

ue w

hen

rubb

ed.

Pyro

clas

tic s

urge

dep

osit.

Poro

us a

ccum

ulat

ions

of

fine

ash-

size

d, a

lter

ed v

itri

c te

phra

, sur

roun

ded

by d

ense

ac

cret

iona

ry a

sh r

ims,

for

m b

ulk

of la

pilli

tuf

f. L

ava

frag

emen

ts:

<5%

. Wea

k ca

lcit

e ce

men

ts:

~30%

ove

rall.

TO

WH

ILL

-06

Tow

er H

ill

crat

er, E

sid

eD

avis

ons

quar

ry

floor

Wea

kly

grai

n su

ppor

ted,

m

oder

atel

y w

ell-

cem

ente

d, p

ale

yello

wis

h br

own

10Y

R 6

/2, p

oorl

y so

rted

vit

ric

tuff

. Has

0.5

to

1 cm

th

ick

laye

rs o

f co

arse

r lit

hic-

crys

tal

teph

ra a

lter

nati

ng w

ith

fine

vitr

ic

teph

ra a

lter

ed t

o cl

ay m

iner

al.

Pyro

clas

tic

surg

e de

posi

t.

Poro

us, a

lter

ed v

itri

c m

atri

x fo

rms

~40%

of

vitr

ic0.

46 li

thic

0.10

cr

ysta

l 0.9

tuff

. Acc

reti

onar

y la

pilli

com

mon

. Lav

a fr

agm

ents

in

coa

rse-

grai

ned

laye

rs: ~

7%.

Wea

k ca

lcit

e ce

men

ts: ~

32%

ov

eral

l. St

rong

wea

ther

ing

to

clay

: 40%

ove

rall.

108 Chris How, Marie Jackson, Catherine Woolfitt

Bell, describing a Cornish miner’s cottage at Burra in South Australia, succinctly sets out the challenge presented by these modest, rustic fabrications:29

How much we know … is usually directly proportional to the number of artifacts … which survive ... the reason we know more about the grand and exceptional buildings … than about the simple ones, is simply because the expensive ones last longer. We know much more about public buildings than dwelling places, although dwellings have always been more numerous.

Raising the profile of these humble pioneer structures by disseminating information about their origins would be significant for their conservation. They are part of the history of the region, albeit linked with the damaging exploitation of the local environment during the period of European settle-ment. Relatively few examples of these volcanic tuff constructions now survive in Victoria, and without conservation measures, this type of structure is at serious risk of gradually disappearing.

AcknowledgementThis paper arose as a result of various dicussions held back in 2006 with Professor John Ashurst, and the authors present this as a tribute to his memory.

Biographies

Chris How, MSc Timber Building ConservationChris How is a structural/civil engineer who has been involved in the conservation of pioneer buildings in south-eastern Australia since 1973. He gained his masters from Bournemouth University (course run in partnership with Weald and Downland Open Air Museum, West Sussex) with a dating system analysis of historic buildings in south-west Victoria.

Marie Jackson, PhD GeologyMarie Jackson carries out research at the History Department of Northern Arizona University into ancient buildings with an emphasis on ancient Roman concrete and volcanic stone construction. She has a dual doctorate awarded in 1987 from Johns Hopkins University (Baltimore, MD, USA) and the Université de Nantes (France).

Catherine Woolfitt, MA Classical Archaeology, MA Art ConservationCatherine Woolfitt is an archaeologist and conservator who trained in Canada. She has worked in the field of art and building conservation in the UK since 1993 and specializes in the conservation of stone and other porous materials in the context of historic buildings, ancient monuments and sculpture. She established Catherine Woolfitt Associates in 2008.

Notes 1 Thomas, J., Illustrated Handbook of Victoria, Australia, John Ferres, Government

Printer, Melbourne (1886). 2 Bonwick, J., Western Victoria: Its Geography, Geology and Social Condition,

Thomas Black, Geelong (1858).

3 Sherwood, J. E., Oyston, B. and Kershaw, A. P., ‘The age and contemporary envi-ronment of Tower Hill Volcano, Southwest Victoria, Australia’, Proceedings, Royal Society of Victoria, Vol. 116, Part 1, 2004, pp. 69–76.

4 Orth, K. and King, R., The Geology of Tower Hill, Victorian Department of Industry, Technology and Resources, Melbourne (1990).

5 Fisher, R. V., Heiken, G. and Hulen, J. B., Volcanoes: Crucibles of Change, Princ-eton University Press, Princeton, CT (1997).

6 Orth and King, op. cit. 7 These are the Qvv deposits of the Warrnambool 1:50000 Geologic Map Series. 8 Orth and King, op. cit. 9 These are the surge deposits which partially filled the ancient Merri River valley.10 Bonwick, op. cit.11 Bonwick, op. cit.12 Bonwick, op. cit.13 Samples from the various buildings were taken by Chris How, and prepared and

analysed by Marie Jackson at the University of North Arizona. Analysis of stone from the south-west plinth of Christ Church in Warrnambool (Table 1, sample CHRCHURCH-02) indicates that it is a fossiliferous tuffaceous sandstone. Ancient flows of the Merri River reworked the sands and deposited them in river terraces, which were quarried alongside outcrops of the Tower Hill tuffs.

14 Bonwick, op. cit.15 Descriptions of tuff masonry are based on extensive field surveys carried out by

Chris How.16 Bonwick, op. cit.17 Bonwick, op. cit.18 Jackson, M. D., Marra, F., Hay, R. L. and Cawood, C., ‘The judicious selection and

preservation of tuff and travertine building stone in ancient Rome’, Archaeometry, Vol. 47, 2005, pp. 485–510.

19 Jackson, M. and Marra, F., ‘Roman stone masonry: Volcanic foundations of the ancient city’, American Journal of Archaeology, Vol. 110, 2006, pp. 403–46.

20 Vitruvius, Vitruvius on Architecture, Books I–IV, translated by Granger, F., Harvard University Press, Cambridge (2002).

21 Jackson, op. cit.22 Jackson and Marra, op. cit.23 Vitruvius, op. cit.24 Jackson, op. cit.25 Török, Á., Gálos, M. and Kocsányi-Kopecskó, K., ‘Experimental weathering of

Rhyolite Tuff building stones and the effect of an organic polymer conserving agent’, Stone Decay: Its Causes and Controls, eds Smith, B. J. and Turkington, A. V., Donhead Publishing, Shaftesbury, 2004, pp. 121–39.

26 Jackson, op. cit.27 Jackson and Marra, op. cit. 28 Vitruvius, op. cit.29 Bell, P., ‘Continuity in Australian timber domestic building: An early timber

cottage at Burra’, Australian Historical Archaeology, Vol. 8, 1990, pp. 3–12.

Maps Colac 1:250000 Geological Map, Sheet SJ 54-11, Geological Survey of Victoria, Melbourne (1996).Portland 1:250000 Geological Map, Sheet SJ 54-11, Geological Survey of Victoria, Melbourne (1997).

Tuff Stone Masonry near Tower Hill in Victoria 109