Building Stone. No artificial building material such as brick, terra-cotta, or cement can give dignity and beauty to an edifice in anything like the same degree as an ordinary limestone or sandstone which can be cut by a chisel. Much less can burnt clay or artificial stone, no matter how much it is enriched by ornament and colour, approach marble, granite, or porphyry, in giving a noble character to an architectural monument.
By far the most common kinds of building stone are sandstones and limestones. The term free-stone is applied indifferently to such examples of both kinds as dress freely with masons' tools. Both are bedded on sedimentary rocks, and both as a rule, when cut up into blocks for building, should be laid on their natural beds. In the northern part of Great Britain the name whinstone is always given by workmen to such igneous rocks as Basalt and Diabase (q.v.); but this name is also applied by them to a sandstone, for example, which has been locally much hardened, as well as to a metamorphosed sedimentary rock such as graywacke.
Sandstone.—Rock of this kind suitable for building is found plentifully in some parts of England, but principally in the central and northern counties, though it also occurs in Devonshire and Monmouthshire. Among numerous quarries it will suffice to name Darley Dale and Bakewell Edge in Derbyshire, Longridge Fell in Lancashire, Viney Hill in Gloucestershire, Bidston Hill in Cheshire, Addingly in Yorkshire, and Hadley in Worcestershire. There are several well-known quarries about Newcastle-on-Tyne, and sandstone of a pleasing red colour occurs at Penrith and other places in Cumberland. These English sandstones are obtained from the Devonian, the Carboniferous, the Permian, and the New Red Sandstone formations. It is from the 'millstone grit' division of the Carboniferous that the stone for many of the public buildings in Manchester, Bradford, and Leeds was obtained. So far as can be judged from the appearance of comparatively modern edifices, the stone stands the smoky atmosphere of these towns very well. Ancient buildings in England, however, do not on the whole show that any sandstone used in them resists decay for centuries. Durham and Chester cathedrals and numerous small churches furnish examples of this.
All the towns of any size in Scotland, except Aberdeen and one or two small places, such as Dalbeattie in Galloway, are built of sandstone. So are almost all the ancient buildings of any note. The stone is chiefly obtained from the Carboniferous and Old Red Sandstone formations, but the
Permian rocks of Cumberland being prolonged into the county of Dumfries, some fine red sandstone is got there from that formation. In Scotland, accordingly, there is ample means of judging of the durability of this building material, which is on the whole so suitable for architectural purposes. It is vexatious in the extreme to have to say that much of the beautiful carved work at Kirkwall, Holyrood, Melrose, Kelso, and Jedburgh is quite wasted by decay. The age of the oldest of these abbeys is but little more than 700 years. Many modern buildings likewise show that, even when believed to be carefully selected, this material is often not durable.
So far as is known, the sandstone from Craigleith Quarry, near Edinburgh, resists atmospheric agencies better than any other in Scotland, or perhaps in the British Islands. A great part of the New Town of Edinburgh has been built of it. More recently, Binny Quarry in Linlithgowshire, the stone from which stands next in quality to Craigleith, has supplied the material for the principal buildings erected in the Scottish metropolis, and to some extent also for buildings in Glasgow; but for some years, owing to the unfavourable state of the quarry, it has yielded only a trifling supply. The cost of working Craigleith is double that of any other Scottish sandstone that would do for a fine building, and consequently no architect has for many years ventured to use it. Binny stone can only be got with difficulty. There are, however, plenty more quarries all through the length and breadth of Scotland, except in the north-west. Strange to say, not one of them, especially in the central part of the country, can furnish a stone upon which an architect can rely as being certainly durable. Yet so strong is the desire to have ornament for merely present appearance, that large quantities of building stones are now being brought from great distances both to Glasgow and Edinburgh, simply because they are of fairly uniform colour and can be cheaply worked.
Sandstones, being composed of grains of quartz, are highly siliceous. Darley Dale contains 96 per cent., Craigleith 97 per cent., and Binny 92 per cent. of silica. Some, however, have not more than 80 per cent. of this substance. The other substances they contain are chiefly carbonate of lime, alumina, and oxide of iron. It is hardly possible to tell a good sandstone merely by chemical analysis. A hard non-porous stone is, of course, more likely to be lasting than one which is soft and porous. There are a number of ancient buildings on or near the banks of the Rhine, between Basel and Cologne, which show the durability of a sandstone in a northern climate better than any in Great Britain. In these it is of a hard nature. See SANDSTONE.
Limestone.—Marble and chalk are the purest limestones, but it will be convenient to notice first those more or less composite limestones which are sufficiently hard and strong for building, yet not highly crystalline like marble. One of the best-known kinds of English building stone is the dolomite, or magnesian limestone of the Permian formation, which ranges from Nottingham to Tyne-mouth. It is a double carbonate of lime and magnesia, containing a varying proportion of silica. At Mansfield in Nottinghamshire, the amount of silica is exceptionally high—viz. 50 per cent., while at Bolsover and Mansfield Woodhouse it is only 4 per cent. The Houses of Parliament are built of this dolomite, which unfortunately decays rapidly under the influence of the London atmosphere. Among ancient buildings, some parts of York Minster show its perishable nature. Yet in Conisborough Castle, built in the 12th century, and in some country churches nearly as old, it has stood the effects of time very well.
The limestone of the oolitic formation, which extends from Dorsetshire into Yorkshire, is obtained for building purposes, for which it is extensively used, at several well-known quarries, such as those of the Isle of Portland, Bath, and Leckhampton Hill in Gloucestershire, Barnac in Northamptonshire, and Ancaster in Lincolnshire. The Bath stone contains 95 per cent. of carbonate of lime; and the Portland stone, which, though belonging to the same formation, is not of oolitic structure, contains the same percentage of that carbonate. The former has besides 2½ per cent. of carbonate of magnesia; the latter 1·2 per cent. of this substance, and the same amount of silica. Small quantities of alumina, iron, and water are present in both. Much of the oolitic limestone is easily cut with a saw when newly quarried, but it hardens on exposure, and is fairly durable. Like the dolomite above mentioned, it is very suitable for enriched as well as plain work, and is of a pleasing colour. Some ancient structures built of the oolitic limestone of their own neighbourhood are in a good state of preservation. Among these are Lincoln Cathedral, some churches at Oxford, and Wells Cathedral. There are others, however, which have not so well resisted decay. St Paul's Cathedral, London, is built of Portland stone. Kentish rag is an impure limestone, compact, heavy, non-absorptive, and difficult to dress. It is used in London chiefly for rubble work, and is very durable.
There are extensive deposits of limestone in England, Scotland, and Ireland, which are only fit for burning into lime, or at least are not suitable for the hevn work of buildings.
The fine limestone from Caen in Normandy is much used for internal architectural work in England, and to some extent even in America. It is a fine-grained, easily chiselled, beautiful material, of a creamy-yellow uniform colour. But in external work it is very liable to decay, especially in towns. In the middle ages it was employed for some cathedrals—that of Canterbury, for example—as well as for smaller churches in the south of England. Travertine is a peculiar kind of limestone believed to be formed by precipitation from water containing lime. It is somewhat cellular in structure, of a buff colour, and very durable in Italy, where, in Rome especially, it has been extensively employed for both ancient and modern buildings, among others the Colosseum and St Peter's. Nummulitic limestone is chiefly composed of beautiful fossils like coins or buttons of filigree work. Some of the Egyptian pyramids are built of this stone. See NUMMULITE.
Marble.—In the British Islands marble is only used for the decorative parts of buildings. White marble is found in Skye, Sutherland, and one or two other places in Scotland. It also occurs in a few localities in Ireland; but it is doubtful whether it would be profitable to work it in either country. Coloured marbles, some of which are handsome, are regularly quarried in Devonshire, and also in Derbyshire, where they contain shells, encrinites, and other fossils, which give them an attractive appearance when polished. Ireland is comparatively rich in coloured marbles. The wavy and mottled green serpentine marble of Connemara is a very beautiful stone. Black marble is worked in Kilkenny and other counties, and a veined red marble in Cork. Italian and other foreign marbles are, however, more used in the United Kingdom than the native kinds. See MARBLE.
Serpentine.—This has a general resemblance to coloured marble, but it is of quite different com- position, being a silicate of magnesia. Cornish serpentine is perhaps the most beautiful ornamental stone in the British Islands. It is principally used for internal decoration. Serpentine is found in Banffshire and in Shetland, but only pieces of limited size can be got. See SERPENTINE.
Granite.—In the granite districts of Great Britain, the stone is used for ordinary building purposes. Aberdeen, for example, is almost wholly built of this material. It is usually only hammer-dressed, but even with the rough face so imparted, it gives a building a good appearance. For decorative purposes it is polished. Peterhead and Ross of Mull are red granites, while the Aberdeen, Dalbeattie, and Creetown varieties are gray or bluish gray. Peterhead granite especially is a good deal used in London and other large towns in the British Islands for some of the more prominent features of buildings, and is also sent to America. The Cornish granites have been much employed for bridges over the Thames, and for docks and breakwaters. There are some good granites in Ireland. See GRANITE, and SYENITE.
United States.—Many excellent building stones are found in America. The quarries of Maine have been the chief source of the supply of granites; and of those from this state the Calais variety is red, and that from Spruce Head gray, both of these taking a fine polish. The granite from Hallowell, also in Maine, is remarkable; as its dressed surfaces are nearly as white as marble. New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, and several other states contain granite. Sandstones constitute the most valuable group of building stones in the United States, as they have a wide distribution, have much diversity of tint and texture, and can be comparatively cheaply obtained. They are principally of triassic and carboniferous age. White marble has been quarried on a considerable scale for important public buildings. That from Lee, Massachusetts, which is strong and durable, was used in the construction of the Capitol at Washington, and for the city hall at Philadelphia. From Stockbridge, in the same state, the marble was got for the state-house at Boston and the city hall of New York. Tuckahoe marble, which is pure white, strong, and coarse-grained, has been employed for some of the finest buildings in New York. For St Patrick's Cathedral a pure white dolomite called 'snowflake marble,' from Pleasantville, New York, has been chiefly used. Rutland county, Vermont, is the great centre of the marble industry for purely decorative purposes. Numerous beautiful coloured marbles have been discovered in the United States during the last thirty years.