CHAP. II. MATERIALS USED IN BUILDING. SECT. I. STONE. 1636. It is not our intention to advert to the stone which the Continent affords for building purposes; a knowledge of the different kinds there found would be of no use to the English architect, and would occupy too much of our space as mere information. It is almost superfluous to say that the choice of stone for a building intended to be durable is of the very highest importance. "In modern Europe," it has been observed, "and particularly in Great Britain, there is scarcely a public building, of recent date, which will be in existence a thousand years hence. Many of the most splendid works of modern architecture are hastening to decay in what may be justly called the infancy of their existence, if compared with the date of public buildings that remain in Italy, in Greece, in Egypt, and the East." 1637. The various sorts of stone take their names either from the places where they are quarried or from the substances which principally enter into their composition. The term "Freestone," which is used in a very arbitrary way, is, as its name implies, that sort which can be wrought with the mallet and chisel, or cut with the saw, an operation which cannot be performed upon granite, whose hardness requires it to be dressed with pointed tools of different weights and sizes. It includes the two great general divisions of Limestone and Sandstone. The limestone of Portland is that which has for many years past been chiefly used in the metropolis. Latterly, other sorts have found their way in from the provinces; and though, from many circumstances, we do not think it likely that Portland stone, from its facility of transport and other causes, will be altogether superseded, there is no doubt that its use is on the wane from the introduction of provincial sorts. 1638. We shall proceed, after some preliminary observations, to give, from the Report lately addressed to the Commissioners of Woods and Forests, on the occasion of selecting the stone for building the new Houses of Parliament, a view of the principal sorts of stone found and used in the island. 1639. The qualities requisite for a building stone are hardness, tenacity, and compactness. It is not the hardest stone which has always the greatest tenacity or toughness; for limestone, though much softer, is not so easily broken as glass. 1640. The decay and destruction of stone are accelerated by nearly the same causes as those which destroy rocks themselves on the surface of the globe. Such causes are of two kinds: those of decomposition and those of disintegration. The former effects a chemical change in the stone itself, the latter a mechanical division and separation of the parts. The effects of the chemical and mechanical causes of the decomposition of stone in buildings are much modified, according to their situation, as, in the town or country. In populous and smoky towns the state of the atmosphere accelerates decomposition more than in those placed in the open country. 1641. "As regards the sandstones that are usually employed for building purposes, and which are generally composed of either quartz or siliceous grains, cemented by siliceous, argillaceous, calcareous or other matter, their decomposition is effected according to the nature of the cementing substance, the grains being comparatively indestructible. With respect to limestones composed of carbonate of lime, or the carbonates of lime and magnesia, either nearly pure or mixed with variable proportions of foreign matter, their decomposition depends, under similar circumstances, upon the mode in which their component parts are aggregated, those which are most crystalline being found to be the most durable, while those which partake least of that character suffer most from exposure to atmospheric influences. 1642. “The varieties of limestones termed Oolites (or Roestones) being composed of oviform bodies cemented by calcareous matter of a varied character, will of necessity suffer unequal decomposition, unless such oviform bodies and the cement be equally coherent and of the same chemical composition. The limestones which are usually termed shelly,' from being chiefly formed of either broken or perfect fossil shells cemented by calcareous matter, suffer decomposition in an unequal manner, in consequence of the shells, which, being for the most part crystalline, offer the greatest amount of resistance to the decomposing effects of the atmosphere. 1643. "Sandstones, from the mode of their formations, are very frequently laminated, more especially when micaceous, the plates of mica being generally deposited in planes parallel to their beds. Hence, if such stone be placed in buildings with the planes of lamination in a vertical position, it will decompose in flakes, according to the thickness of the lamina; whereas, if it be placed so that the planes of lamination be horizontal, that is, most commonly upon its natural bed, the amount of decomposition will be comparatively immaterial. 1644. "Limestones, such at least as are usually employed for building purposes, are not liable to the kind of lamination observable in sandstones; nevertheless, varieties exist, especially those commonly termed shelly, which have a coarse laminated structure, generally parallel to the planes of their beds, and therefore the same precaution in placing such stone in buildings so that the planes of lamination be horizontal, is as necessary as with the sandstones above noticed. 1645. "The chemical action of the atmosphere produces a change in the entire matter of the limestones, and in the cementing substance of the sandstones acccording to the amount of surface exposed to it. The mechanical action due to atmospheric causes occasions either a removal or a disruption of the exposed particles, the former by means of powerful winds and driving rains, and the latter by the congelation of water forced into or absorbed by the external portions of the stone. These effects are reciprocal, chemical action rendering the stone liable to be more easily affected by mechanical action, which latter, by constantly presenting new surfaces, accelerates the disintegrating effects of the former. 1646. "Buildings in this climate are generally found to suffer the greatest amount of decomposition on their southern, south-western, and western fronts, arising doubtless from the prevalence of winds and rains from those quarters; hence it is desirable that stones of great durability should at least be employed in fronts with such aspects. 1647. " Buildings situated in the country appear to possess a great advantage over those in populous and smoky towns, owing to lichens, with which they almost invariably become covered in such situations, and which, when firmly established over their entire surface, seem to exercise a protective influence against the ordinary causes of the decomposition of the stone upon which they grow. 1648. "As an instance of the difference in degree of durability in the same material subjected to the effects of the atmosphere in town and country, we may notice the several frusta of columns and other blocks of stone that were quarried at the time of the erection of St. Paul's Cathedral in London, and which are now lying in the island of Portland, near the quarries from whence they were obtained. These blocks are invariably found to be covered with lichens, and although they have been exposed to all the vicissitudes of a marine atmosphere for more than 150 years, they still exhibit, beneath the lichens, their original forms, even to the marks of the chisel employed upon them, whilst the stone which was taken from the same quarries (selected, no doubt, with equal, if not greater, care than the blocks alluded to) and placed in the cathedral itself, is, in those parts which are exposed to the south and south-west winds, found in some instances to be fast mouldering away. Colour is of more importance in the selection of a stone for a building to be situated in a populous and smoky town, than for one to be placed in an open country, where all edifices usually become covered, as before stated, with lichens; for although in such towns those fronts which are not exposed to the prevailing winds and rains will soon become blackened, the remainder of the building will constantly exhibit a tint depending upon the natural colour of the material employed. 1649. "Before we proceed to adduce a few examples of the present condition of the various buildings we have examined, we would wish to observe that those which are highly decorated, such as the churches of the Norman and pointed styles of architecture, afford a more severe test of the durability of any given stone, all other circumstances being equal, than the more simple and less decorated buildings, such as the castles of the fourteenth and fifteenth centuries, inasmuch as the material employed in the former class of buildings is worked into more disadvantageous forms than in the latter, as regards exposure to the effects of the weather; and we would further observe, that buildings in a state of ruin, from being deprived of their ordinary protection of roofing, glazing of windows, &c., constitute an equally severe test of the durability of the stone employed in them. 1650. "As examples of the degree of durability of various building stones in particular localities, the following may be enumerated. Of the sandstone buildings which we examined, we may notice the remains of Ecclestone Abbey, of the thirteenth century, near Barnard Castle, constructed of a stone closely resembling that of the Stenton quarry in the vicinity, as exhibiting the mouldings and other decorations, even to the dog's-tooth ornament, in excellent condition. The circular keep of Barnard, apparently also built of the same material, is in fine preservation. Tintern Abbey may also be noticed as a sandstone We must take leave to question this statement; as, for instance, in St. Paul's Cathedral we find the northern front peculiarly black, whilst the south front and south-western angle are comparatively white. This we have always considered to have arisen from the more constant action of the sun's rays upon them. edifice that has to a considerable extent resisted decomposition; for although it is decayed in some parts, it is nearly perfect in others. Some portions of Whitby Abbey are likewise in a perfect state, whilst others are fast yielding to the effects of the atmosphere. The older portions of Ripon Cathedral, constructed of sandstone, are in a fair state of preserv ation. Rivaulx Abbey is another good example of an ancient sandstone building in a fair condition. The Norman keep of Richmond Castle in Yorkshire affords an instance of a moderately hard sandstone which has well resisted decomposition. 1651. "As examples of sandstone buildings of more recent date in a good state of preservation, we may mention Hardwicke Hall, Haddon Hall, and all the buildings of Craigleith Stone in Edinburgh and its vicinity. Of sandstone edifices in an advanced state of decomposition we may enumerate Durham Cathedral, the churches at Newcastle upon Tyne, Carlisle Cathedral, Kirkstall Abbey, and Fountains Abbey. The sandstone churches of Derby are also extremely decomposed; and the church of St. Peter at Shaftesbury is in such a state of decay that some portions of the building are only prevented from falling by means of iron ties. 1652. "As an example of an edifice constructed of a calciferous variety of sandstone, we may notice Tisbury Church, which is in unequal condition, the mouldings and other enrichments being in a perfect state, whilst the ashler, apparently selected with less care, is fast mouldering away. 1653. "The choir of Southwell Church, of the twelfth century, may be mentioned as affording an instance of the durability of a magnesio-calciferous sandstone, resembling that of Mansfield, after long exposure to the influences of the atmosphere. 1654. “Of buildings constructed of magnesian limestone we may mention the Norman portions of Southwell Church, built of stone similar to that of Bolsover Moor, and which are throughout in a perfect state, the mouldings and carved enrichments being as sharp as when first executed. The keep of Koningsburgh Castle, built of a magnesian limestone from the vicinity, is also in a perfect state, although the joints of the masonry are open in consequence of the decomposition and disappearance of the mortar formerly within them. The church at Hemmingborough, of the fifteenth century, constructed of a material resembling the stone from Huddlestone, does not exhibit any appearance of decay. Tickhill Church, of the fifteenth century, built of a similar material, is in a fair state of preservation. Huddlestone Hall, of the sixteenth century, constructed of the stone of the immediate vicinity, is also in good condition. Roche Abbey, of the thirteenth century, in which stone from the immediate neighbourhood has been employed, exhibits generally a fair state of preservation, although some portions have yielded to the effects of the atmosphere. 1655. As examples of magnesian limestone buildings in a more advanced state of decay, we may notice the churches at York, and a large portion of the Minster, Howden Church, Doncaster Old Church, and others in that part of the country, many of which are so much decomposed that the mouldings, carvings, and other architectural decorations are often entirely effaced. 1656. "We may here remark, that, as far as our observations extend, in proportion as the stone employed in magnesian limestone buildings is crystalline, so does it appear to have resisted the decomposing effects of the atmosphere; a conclusion in accordance with the opinion of Professor Daniell, who has stated to us that from the results of experiments, he is of opinion the nearer the magnesian limestones approach to equivalent proportions of carbonate of lime and carbonate of magnesia, the more crystalline and better they are in every respect.' 1657. "Of buildings constructed of oolitic and other limestones, we may notice the church of Byland Abbey, of the twelfth century, especially the west front, built of stone from the immediate vicinity, as being in an almost perfect state of preservation. Sandysfoot Castle, near Weymouth, constructed of Portland oolite in the time of Henry VIII., is an example of that material in excellent condition; a few decomposed stones used in the interior (and which are exceptions to this fact) being from another oolite in the immediate vicinity of the castle. Bow and Arrow Castle, and the neighbouring ruins of a church of the fourteenth century, in the Island of Portland, also afford instances of the Portland oolite in perfect condition. The new church in the island, built in 1766, of the variety of the Portland stone termed roach, is in an excellent state throughout, even to the preservation of the marks of the chisel. 1658. " Many buildings constructed of a material similar to the oolite of Ancaster, such as Newark and Grantham Churches, and other edifices in various parts of Lincolnshire, have scarcely yielded to the effects of atmospheric influences. Windrush Church, built of an oolite from the neighbouring quarry, is in excellent condition, whilst the Abbey Church of Bath, constructed of the oolite in the vicinity of that city, has suffered much from decomposition; as is also the case with the cathedral, and the churches of St. Nicholas and St. Michael in Gloucester, erected of a stone from the oolitic rocks of the neighbour. hood. 1659. The churches of Stamford, Ketton, Colley Weston, Kettering, and other places in that part of the country, attest the durability of the Shelley oolite, termed Barnack Rag, with the exception of those portions of some of them for which the stone has been illselected. The excellent condition of those parts which remain of Glastonbury Abbey show the value of a shelly limestone similar to that of Doulting, whilst the stone employed in Wells Cathedral, apparently of the same kind, and not selected with equal care, is in parts decomposed. The mansion, the church, and the remains of the abbey at Montacute, as also many other buildings in that vicinity, constructed of the limestone of Ham Hill, are in excellent condition. In Salisbury Cathedral, built of stone from Chilmark, we have evidence of the general durability of a siliciferous limestone; for, although the west front has somewhat yielded to the effects of the atmosphere, the excellent condition of the building generally is most striking. 1660." In the public buildings of Oxford, we have a marked instance both of decomposition and durability in the materials employed; for whilst a shelly oolite, similar to that of Taynton, which is employed in the more ancient parts of the cathedral, in Merton College Chapel, &c., and commonly for the plinths, string-courses, and exposed portions of the other edifices in that city, is generally in a good state of preservation, a calcareous stone from Heddington, employed in nearly the whole of the colleges, churches, and other public buildings, is in such a deplorable state of decay, as in some instances to have caused all traces of architectural decoration to disappear, and the ashler itself to be in many places deeply disintegrated. 1661. "In Spofforth Castle we have a striking example of the unequal decomposition of two materials, a magnesian limestone and a sandstone; the former employed in the decorated parts, and the latter for the ashler or plain facing of the walls. Although the magnesian limestone has been equally exposed with the sandstone to the decomposing effects of the atmosphere, it has remained as perfect in form as when first employed, while the sandstone has suffered considerably from the effects of decomposition. 1662. "In Chepstow Castle, a magnesian limestone in fine preservation, and a red sandstone in an advanced state of decomposition, may be observed, both having been exposed to the same conditions as parts of the same archways; and in Bristol Cathedral there is a curious instance of the effects arising from the intermixture of very different materials, a yellow limestone and a red sandstone, which have been indiscriminately employed both for the plain and decorated parts of the building; not only is the appearance in this case unsightly, but the architectural effect of the edifice is also much impaired by the unequal decomposition of the two materials, the limestone having suffered much less from decay than the sandstone. 1663. " Judging, therefore, from the evidence afforded by buildings of various dates, there would appear to be many varieties of sandstone and limestone employed for building purposes which successfully resist the destructive effects of atmospheric influences; amongst these the sandstones of Stenton, Whitby, Tintern, Rivaulx, and Cragleith, the magnesio-calciferous sandstones of Mansfield, the calciferous sandstone of Tisbury, the crystalline magnesian limestones, or Dolomites of Bolsover, Huddlestone and Roche Abbey, the oolites of Byland, Portland, and Ancaster, the Shelly oolites and limestones of Barnack and Ham Hill, and the siliciferous limestone of Chilmark appear to be amongst the most durable. To these, which may all be considered as desirable building materials, we are inclined to add the sandstones of Darley Dale, Humbie, Longannet, and Crowbank, the magnesian limestones of Robin Hood's Well, and the oolite of Ketton, although some of them may not have the evidence of ancient buildings in their favour." The Report upon which we have drawn so largely, and from which we shall extract still larger drafts, then proceeds to close by a preference to limestones on account "of their more general uniformity of tint, their comparatively homogeneous structure, and the facility and economy of their conversion to building purposes," of which it prefers the crystalline; on which account, and its combination with a close approach to the equivalent proportions of carbonate of lime and carbonate of magnesia, for uniformity in structure, facility and economy in conversion, and for advantage of colour, the parties to the Report prefer the magnesian limestone or dolomite of Bolsover Moor and its neighbourhood. The Report deserves every commendation. There are points which, were we disposed to cavil, might furnish matter for it, but upon the whole it has been well done, and is the first scientific step the government of this country has ever taken in respect of practical architecture. 1664. The following table presents a synoptical, and, to the architect, important view of the relative value, in every respect, of the principal species of stone which the various provinces of England afford for building purposes, and is condensed from the Report so much at length above quoted. |