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THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



fJuLY, 



It is rather remarkable that the revival of the manufacture of terra 

 cotta, or more projierly of artificial stone, in England, should have 

 been effected by a lady. About sixty years ago. Miss Coade, from 

 Lyme Regis, possessing a large share of scientific knowledge and 

 energy, embarked in a small manufactory of artificial stone in Lam- 

 beth, tt hich, by her perseverance and good management, eventually 

 attained a considerable degree of celebrity. To this original 

 estalilishment in Lambeth the merit is due of greatly improving 

 the composition of the material, and the processes by which its 

 permanent character was attained. The proprietor had also suffi- 

 cient enterprise and discrimination to avail herself of the talents of 

 gome distinguished artists, and thus produced works of a superior 

 character, which may fairly vie with tliose of the chisel. The 

 l)as-relief in the pediment over the western portico at Greenwich 

 Hospital, representing the Death of Nelson, was designed by West, 

 and executed by Bacon and Panzetta, who also modelled many 

 other distinguished works. 



With respect to modern instances of the use of artificial stone, St. 

 Pancras Church may be considered as one of the most important; the 

 greater part of the ornamental details being formed of this mate- 

 rial, at the large outlay of 54-00/. The work was executed by Mr. 

 Rossi, from the designs of Mr. Inwood, the architect: and, ac- 

 cording to jiresent appearances, the material promises to be very 

 durable. About the same time extensive bas-reliefs, colossal 

 figures, and other decorations, executed in the same material, 

 were placed on the front of the Custom House, London, hut these 

 specimens have been removed. The statue of Britannia, made of 

 artificial stone, which crowns the Nelson column at Yarmouth, 

 remains uninjured by the exposure, to which the stone work seems 

 to be yielding. The Bau-Akademia, in Berlin, by Hcliinkel, is a 

 remarkable exami)Ie of the modern adaptation of moulded brick 

 and terra-cotta, of which every part, even the face of the w alls, is 

 most carefully wrought : -id finished. 



Having taken a general view of the history of the art in ques- 

 tion, and its application in various ages and countries, it may be 

 proper to give some account of the composition and modes of 

 forming and perfecting the artificial stone as now practised. It 

 has been already stated that the ancient examples are evidently 

 formed simply of fine clay, or brick earth — carefully prepared and 

 well burnt — and they are, therefore, precisely of the same nature 

 as coarse pottery ware, and are correctly designated "Terra-cotta;" 

 but the modern artificial stone is a very different substance, and 

 greatly superior to them in hardness, texture, and colour. The 

 result of inquiry at several establishments shows that some differ- 

 ence exists, both in the composition and processes adopted by the 

 respective manufacturers, but without any obvious difference in 

 the results, 'I'he i>rinci])al ingredient is the white potter's clay, 

 forming about one-half; pulverised stone ware from one-third to 

 one-fifth; ditto glass, from one-fourth to one-ninth; and some 

 add, for finer purposes, a small portion of white llyegate sand and 

 lioivdered flint, about one-tenth part of each; these ingredients are 

 carefully mixed in a pug-mill to a stiff consistence suitable for 

 modelling or moulding, and then worked into the various fornis 

 required. With a view to ensure perfect burning, an uniform 

 thickness must be preserved in all parts, usually about l^inch, 

 l>ut i)roportionate to the bulk and strength re(iuired; considerable 

 attention is necessary in the process of drying that it should be 

 slow and regiila.'-, so as to avoid any distortion of form; the time 

 to be allowed must, in some measure, be governed by the state of 

 the atmosphere and other circumstances. The same considerations 

 regulate the burning, which should proceed by very slow degrees 

 to a white heat, and ample time should be allowed for cooling: the 

 jiractice in tliese respects — wliicli appears to vary very widely in 

 different manufactories — allows from ten to fourteen days for dry- 

 ing, from seven to fourteen for burning, and tliree or four days for 

 cooling. 



'i'he kiln at Messrs. W. Cuhitt and Co.'s, which may be taken as 

 an ordinary example, is a cylinder of 10ft. Gin. diameter externally, 

 and 10 feet high to tlie base of the cone. The enclosing wall is 

 two bricks thick, having a large opening for packing and unpack- 

 ing the articles to be burnt. M'hen the kiln is filled, this is closed 

 up with lumps, preparatory to lighting tiie furnaces. The interior 

 is lined with tiles .',-iiicli tliick, grooved and tongued together, and 

 set in Stourbridge clay, leaving a vacancy of 1 inches, which is 

 called the nniffling, all round. I'here are two furnaces, and about 

 three tons of coals (Hartley's) are consumed in one l)urning. Tlie 

 progress of the burning is ascertained by looking through an 

 inspection-hole with a lens in the side of the kiln. 



Having been led to tlie cousideration of this subject with a view 

 to its practical application, I venture to adduce some instances in 



which I have used artificial stone, combined with other materials, 

 in the construction of cornices, which, at the same time, serve the 

 purpose of eaves gutters. The advantages proposed in these cases 

 were lightness and strength, with durability and economy. In 

 one example here exhibited, it will be seen that, as a mere corona 

 of the cornice, it gives apparent magnitude to the elevation, with 

 very slight addition of substance or weight. The material, from 

 its hardness and imperishability, is best suited to the situation 

 where it is most exposed to injuries. It also forms a rim, or mar- 

 gin, which throws back the water instead of allowing it to run 

 down over the face of the mouldings in the usual way, in which the 

 top slopes outwards; and by which, in a smoky atmosphere, the 

 cornice is liable to be much defaced and injured. Another example 

 refers to the cornice of a pediment, therefore it is independent of 

 any gutter. In another example the gutter is at the back of the 

 cornice, and is of a distinct construction. In another the gutter 

 is contained within the facia and crown mould, forming a continued 

 trough, resting on a course of slate slabs, which constitute the 

 soffit of the cornice. And, in the last example, the gutter forms 

 a separate portion, lapping over a facia, which is also of artificial 

 stone; and the whole is supported on slate slabs, as the preceding 

 one. The several parts are united lengthwise, by rebated joints, 

 set in white lead, and bedded in cement on the brick and slate. 

 The Greek examples, before alluded to, first led me to this prac- 

 tical application of terra-cotta. It should be observed, that the 

 chief difficulty in preparing this material for the several purposes 

 mentioned, is its liability to become distorted in drying and burn- 

 ing. To avoid tliis it is necessary that the pieces should be short 

 in proportion to their width; and then the deflections (which in 

 some degree are unavoidable) may be so adjusted in setting as not 

 to be conspicuous; and as the cornice is the part most remote from 

 inspection, the imperfection is the less observable. Further, it 

 may be presumed, that if the use of artificial stone were more 

 general, and occasioned consequently a greater demand for this 

 description of work, some means would no doubt be found for 

 rendering the manufacture more perfect. In order to obtain a fall 

 or current in the trough gutters, the bottoms are partially filled 

 up with Portland cement having the greatest thickness towards the 

 centre, and gradually diminished to the outlets. This, besides 

 facilitating the discharge of the rain w ater, serves to strengthen 

 the construction, by covering the joints and fortifying the sides. 

 The colour of artificial stone assimilates tolerably well with Port- 

 land or Caen stone, but the texture is liable to have too much of 

 the glare of pottery. Its durability, if properly manufactured, 

 maj' be deemed almost unlimited, and its economy, if judiciously 

 applied, is a further recommendation; but this involves many 

 important considerations for the judgment and discretion of the 

 architect. 



Although these remarks have properly been limited to terra-cotta 

 and artificial stone, which, as the designation of the first implies, 

 have to undergo the action of fire; yet, as the latter is now a])plied 

 to a material prepared by a different process, it may not be irrele- 

 vant to make some mention of it on the present occasion. It 

 appears that this substance consists of a concrete, formed with 

 cement and sand, variously proportioned, and the forms are pro- 

 duced from moulds; consequently one of its chief advantages is 

 economy, where uumerous repetitions are required. If a nice finish 

 is desired, these productions can be worked up and sharpened by 

 the chisel. 



This art has been practised for about twenty years; but it is 

 more particularly within the last ten years that it has been brought 

 into very extensive use: the experience, therefore, of its durability 

 is, at present, rather limited; but, at all events, great credit is 

 due to the manufacturers, for the taste evinced in many of their 

 productions, wliich constitute another resource, in cases where the 

 works of the sculptor would he excluded by their great expense. 



Reverting to terra-cotta, I beg, in conclusion, to observe, that it 

 may be seen from what has been stated, that it possesses many 

 valuable qualities and recommendations when introduced with skill 

 and discrimination — viz., strengtii, durability, and economy; more 

 particularly where high relief and sharpness are required, and for 

 l>arts extensively repeated. That it affords the most perfect oppor- 

 tunity for the development of artistic talent in the higher branches 

 of art, inasmuch as the model in this case becomes the original and 

 ]iermanent work; embodying in all its freshness the original touch 

 and conception of the artist. Further, and in regard to structural 

 considerations, that it may be combined with other materials, so as 

 to afford increased means and facilities for giving architectural 

 expression with sound construction and eccuomy. 



