Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/521

Rh BUILDING STONES.] BUILDING 469 ?tieous jcks. ranite. each 2 feet 3 inches deep and 14 inches wide, running across from side to side, on which rails were fixed to carry a travelling platform of the whole width which went the reverse way. To one side of the first named timbers was suspended a platform which carried the machinery for raising the materials from the bottom up the central shaft ; they were then raised on to the traveller which carried them at once to the required spot for fixing. When a certain height of work had been done, the huge timbers were raised by six screw-jacks working together, and rested on the new wall, the jacks being removed and prepared for another raising when necessary. The Victoria Tower was erected on a somewhat similar principle, but having two travellers working upon a circular tramway on a strong trussed framing, the ends of each secured to a central drum. To raise the materials a strong under-trussed parallel framing was formed on one side, which brought them up on the outside of the tower. Stones used in Building. It may be useful to give a list of the stones principally used in building, according to their geological formation, with some practical remarks upon each. Of igneous rocks of volcanic origin, the varieties which are used on the continent of Europe are those light stones called tufa and pumice, and the stone called peperino. The two former were extensively employed by the Romans in the tilling in of vaulting, on account of their great lightness. The latter stone, which is obtained in large quantities near Rome, was used by that people extensively, particularly for substructures, being obtained in large blocks. Of the second division of igneous rocks, the trappcan, porphyry and serpentine have been used, but chiefly as ornamental coloured stones, and have been generally classed as marbles. Of the third division, the supersilicatcd rocks, granite alone is now extensively employed, not only in engineering works, but in public buildings and dwellings. It is got from the quarries by splitting the blocks with wedges, and is so hard that it cannot be cut by any ordinary saws. It has to be worked first with large hammers, and then reduced by pointed chisels, and consequently is very expen sive in building. Machinery is used very largely in cutting and also in polishing it. Some very good specimens come from Corn wall and Devonshire, but by far the best are from Dundee and Aberdeen. A variety of the latter, called Peterhead granite, is only to be equalled by the finest Oriental granites. The Kingstown granite from near Dublin is much used locally. Of the aqueous rocks, mechanically formed, and of the arenaceous varieties, gravel is used for concrete, and sand in making mortar, ndstones. Sandstones and gritstones are very extensively used. These are either laminated, as the York stone, used generally for paving, as it can readily be split into large surfaces of small relative thick ness, or compact, as Old Red Sandstones, which stand very well in ternally, but perish sadly with the weather, as may be seen at Chester Cathedral. The New Sandstones, the best of which is the Calverley stone got near Tunbridge Wells, are easily quarried, but if sawn, the wet saw and sand must be used. The finer grained compact sandstones, which are comparatively free from iron, and form very good building-stones, are very numerous. Such are the Bramley Fall, used for bridge copings, plinths, &c. ; the Park Spring, Elland Edge, Whitby, and others, all in Yorkshire ; the Hollington in Staffordshire ; the Mansfield in Nottinghamshire ; and the Minera quarries at Wrexham. A bed of the last is much used at Chester and Liverpool for building purposes, and it has just been introduced into the London market, for which city it is thought it will be very eligible, on account of its lasting qualities ; it has been also used at the National Safe Deposit Company s offices in London. Scotland can boast of some of the finest quarries of sandstone, the best, perhaps, being the Craigleith, much used at Edinburgh. The College, courts of law, Register House, Custom house, Royal Exchange, National Monument, and many churches and private residences there, are built of this excellent material, which has also been extensively exported to Hamburg, Altona, Gothenburg, and other places. Humbie stone has also been much used, both at Edinburgh and at Glasgow, where it fqrms the Royal Exchange and Royal Bank ; it is easier to work than Craigleith. Glamis is also a fine sandstone ; the castle there, as well as those at Inverquharity and Cortachy, and Lindertis House, are built of this material. In Fifeshire, at Cullalo, are quarries whence the stones for the monument to Lord Melville at Edinburgh, and that to Lord Nelson at Yarmouth, were obtained. In addition to beauty and durability, these stones have the merit of being capable of re ceiving the finest and smoothest forms from the chisel of the work man. Another class of sandstones are commonly called firestoncs, as they endure the action of fire better than most others. Of these the best known is the Reigate stone, which is the principal material jiieous
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used at Windsor Castle, Hampton Court, and in many old buildings round London. The Minera stone already mentioned is another. Of mechanically-formed aqueous stones classed as argillaceous, the Clunch. Chinch only is used in building. It may be seen in Ely and Peterborough cathedrals, and many other mediaeval buildings, and is a beautiful material for interior carved work, but will not stand the weather. Of the aqueous stones classed as chemically formed, there is Travertine, none of note but the Travertine, or, properly speaking, Tiburtine. This is a coarse grained stone, of warm colour, found in large blocks, and extensively used at Rome, both in ancient and modern build ings, of which the cathedral of St Peter s may be cited as an instance, but it is unknown in England. Of aqueous rocks, organically derived, the calcareous claim prin- Limestones, cipal attention. The chief of these are the limestones, which are classed as compact, magnesian, or oolitic limestones. Of the first, Compact the best, in the south of England, is that called Chilmark, of which limestone*. Salisbury Cathedral and Wilton Abbey, and many other fine build ings, have been erected. In the Midland counties the Tottenhoe stone, of which Dunstable Priory, Woburn Abbey, Luton church, &c., are built, is an excellent stone. There is also a stone of high quality got at Hopton Wood, near Worksworth in Derbyshire, used at Chatsworth, Belvoir, Drayton Manor, &c. Ancaster stone, near Sleaford in Lincolnshire, has been used for a number of years ; also Ham Hill, near Yeovil, in Somersetshire. Of magnesian lime- Magnesian stones we may name the Anston and Bolsover Moor stones, used limestones, formerly at Southwell Minster, and lately at the Houses of Parlia ment ; the Tadcaster stones, used at York, Beverley, and Ripon Minsters, and very many other buildings ; the Roche Abbey, used at the building of that name, and very many other churches in York shire and Lincolnshire ; the Brodsworth, near Doncaster ; and the Huddlestone, near Sherburne in Yorkshire. These stones contain a great deal of carbonate of magnesia, from which they take their name, are of beautiful texture, and stand well in the country as building stones, but fail in London. A very excellent limestone for rough walling, especially for Gothic work, is that called Kentish Rag. It is found in large quantities in Kentish the neighbourhood of Maidstone ; it is very hard, and is worked Rag. with large hammers instead of the saw. Jambs, strings, and mould ings are sometimes worked of it, but the hardness makes the work expensive ; these, as well as the quoin stones and dressings, are therefore formed of Caen or Bath or other local stones. Kentish Rag does not answer for interior work. The most important subdivision of the limestones used in masonry Oolitic is the Oolitic. They are so called because they resemble, when stones, broken, a conglomerate of globular eggs ; they are also named roe- stones, from their resemblance to what is called the hard roe of a fish. Very good examples of these are the Bamack stone from Northamp tonshire, of which Peterborough Cathedral, Croyland Abbey, Bur- leigh House, &c., are erected, and the Ketton stone, used at most of the colleges in Cambridge, and at Bury St Edmunds, Bedford, Stamford, Doulting in Somersetshire, and at Wells Cathedral and surrounding churches. But the principal English oolites used in masonry are the Bath and the Portland. The former, as its name Bath imports, is found in the neighbourhood of Bath. The chief quarries stone, are the Box Hill, Combe Down, Farleigh Down, and Corsham Down ; all these quarries vary in quality at different depths. The Corsham Down is said to produce the finest in quality, and the Box Ground stone to be the hardest ; but everything in the use of this stone depends on the bed selected. Large quantities of a similar stone are imported from Caen, in Normandy. This is more compact in tex ture than Bath, and therefore fitter for carving, but does not appear to stand our climate so well. The best variety of this stone is said to be the D Aubigny stone. Almost all these oolites can be sawn with a common dry saw, which saves a great deal in the labour of conversion. But, without doubt, the best of all this class of stones is that from the Island of Portland ; for beauty of texture, and for Portland durability, it perhaps exceeds any stone in the world. It seems the stone, only one unaffected by the smoke of London ; and therefore the greater number of its buildings, St Paul s among the rest, are of this stone. Being of hard texture, however, it must be sawn by the use of sand and water, and is much more expensive to work than the softer oolites. There are between fifty and sixty quarries on the island. The best are said to be those on the north-eastern side ; but, as with all stones, there is good and bad in every quarry, and everything depends on the selection. It is said that when Sir Christopher Wren built St Paul s Cathedral, he had this stone quarried and exposed to the weather on the sea-beach for three years, before he suffered it to be used. Of siliceous stones, flint is sometimes used for rough walling and Siliceous for ornamental facing with brickwork ; but in England this work stones, is done by the bricklayer, and not the mason. The only remaining class is that of the mctamorphie rocks, of Metamor- which the crystalline or saccharine and the serpentinous limestone phic rocks are used ; but these are all species of marbles, used more as orna- or marbles, mental than as constructive building-stones, and need not b dwelt upon here.