hotels in the counties above mentioned (Derbyshire, West Riding, N. Lancashire, Westmoreland, Glamorganshire, &c.), are constructed of them; and in Ireland they have been similarly used from the time of the round towers downwards. Perhaps they appear to most advantage, whether in tooled courses or in rustic work, when accompanied by sandstone corners, rybats, and lintels. But even without these adjuncts, when their colour is light, and proper care bestowed on the size, arrangement, and tooling of the courses, they make handsome structures in the pure air of the country, as may be seen in several of the old castles, churches, and public buildings in the districts above referred to.

The limestones of the Permian System are mainly Magnesian -that is, consist of carbonates of lime and magnesia, with varying proportions of silica, alumina, and iron. If the silica is in excess they become calcareous sandstones, generally of hard and close texture; but when it constitutes only a small percentage, they are regarded as magnesian limestones. Many limestones in other formations contain small amounts of magnesia, but only those containing above 15 or 18 per cent are entitled to the name of " Magnesian." The more crystalline or dolomitic they are in texture, the more durable they become; and those are most to be relied upon in which the lime and magnesia occur in nearly equivalent proportions. Generally, however, they exhibit great variety of texture and composition, even in the same quarry, and therefore require very careful and skilled selection. They derive their warm yellowish tints from the oxide of iron, assuming deeper tints as that ingredient prevails. In specific gravity they vary from 2 to 2.66; are much more absorbent of water than the sandstones; weigh from 128 lb. to 152 lb. a cubic foot; and, in the more crystalline varieties, withstand a considerable crushing power. The following are analyses as given in the Commissioners' Report on BuildingStones, and by Richardson :

In England (for they do not occur either in Scotland or Ireland) these magnesian limestones occupy considerable areas in Durham, Yorkshire, Derby, and Notts, and appear in many varying beds (earthy, laminated, compact, concre

tionary, and crystalline), the whole series being from 200 to 300 feet in thickness. In Durham they are seldom used as building-stones, unless for rude walls and inferior structures. In Yorkshire they are, and have been, more largely raised at various places near Tadcaster, Sherborne, Doncaster, and Auston, and employed in various structures, but generally with varying results, as may be witnessed in the ecclesiastical buildings of York, Doncaster, Hull, Beverley, Selby, Ripon, and various parts of Lincolnshire. In Derbyshire the Bolsover Moor quarries, employed in the new Houses of Parliament, yield stones of varying quality-some wasting and worthless, and others of fair durability. On the other hand, the celebrated quarries of Mansfield, in Nottinghamshire, yield a silicious dolomite, of hard, close-grained, and enduring texture. Few rocks, indeed, vary so much in texture and durability as the magnesian limestones of England. In the same quarry, beds of tried excellence are frequently associated with others which look as well, but are worthless; hence the skilled and watchful care that is requisite in selection. It is not only that they differ in composition-the magnesia ranging from 45 down to 10 per cent and under-but that they vary in textural aggregation from hard, compact, and crystalline beds to others that are so soft and earthy as to yield readily to the nail.

The Oolitic limestones or calcareous freestones of the Jurassic System are largely employed for architectural purposes in the midland and southern counties of England, being pleasing in colour, easily raised and tooled, and of fair durability when close-grained and homogeneous in texture. They are generally of whitish, cream-coloured, or light-brown tints; vary in texture from compact small-grained roestones to peastones, and from peastones to coarse-grained, shelly, and coralline ragstones; can be raised in blocks of any size; and though soft when newly quarried, acquire hardness and toughness on exposure. Occurring in four zones of the system-the Inferior Oolite, the Great or Bath Oolite, the Coralline Oolite, and the Portland stone-they necessarily present great variety of colour and quality; hence it is only the denser and finer-grained beds that are worked in their respective localities.

The Inferior Oolite, which is largely developed in the Cotswold Hills, yields some fine-grained, compact, white or light-yellow beds, that are quarried at many places along the range-Leckhampton near Cheltenham, Painswick, Breckhampton, Ingleborough, &c. The Bath Oolite is still more

largely quarried, as well as raised from subterranean workings, along the Somerset and Wiltshire hills-Stroud, Box, Chippenham, Doulting, &c.—and yields a fine, close-grained, whitish stone, which can be raised in blocks of any size, and though soft enough when first extracted to be cut with the saw, yet soon hardens on exposure. As this zone trends eastward through Oxfordshire, Northamptonshire, and Lincolnshire, it assumes browner and richer tints, and is quarried at several localities-the quarries of Barnac and Casterton in Northamptonshire, of Ketton near Stamford, Haydor near Grantham, and Ancaster near Sleaford, being often referred to as yielding blocks of great size, pleasing tints, and tried durability. The Coralline Oolite, being inferior in texture and durability, is seldom used as a building-stone; but the Portland Beds have been long and largely quarried, and extensively employed in most of the public structures of London (St Paul's Cathedral and other churches), and in several of those of Dublin, as well as in many of the more important buildings in the south of England. When the Commissioners reported, in 1839, there were 56 quarries in the island, employing 240 quarrymen, and raising annually about 24,000 tons of stone; and notwithstanding the greater competition with the Bath oolites, the demand, we believe, still continues.

Throughout the whole zone of these Oolites, which stretches, in varying breadth, from Dorset to Scarborough, they have been, and are still, extensively employed in ecclesiastical structures, manor-houses, and public edifices in towns. When carefully selected, and not exposed to the carbonated atmosphere of cities and manufacturing towns, many of them are of fair durability; but even the best of them are not to be compared in this respect with the silicious grits and sandstones. For internal purposes, however, their pure colours, their lightness, and the facility with which they can be carved, render them especially adapted; hence the extensive use of such fine-grained varieties as those of Painswick, Box, and Caen in Normandy. In specific gravity the Oolites vary from 2 to 2.5; a cubic foot weighs, when dry, from 125 to 150 lb.; when dry they absorb from 8 to 10 per cent of their weight of water; and in composition they are nearly pure carbonates of lime with minor proportions of carbonates of magnesia, silica, and iron. That of Bath, according to Daniell and Wheatstone,* consists of carb. lime 94.52, carb. mag. 2.50, iron and alumina 1.20, water and loss 1.78; and that of Portland,

Report of Commissioners on Building-Stones.

carb. lime 95.16, carb. mag. 1.20, silica 1.20, iron and alumina 0.50, water and loss 1.94.

With the exception of the compact calcareous stone from Beer, in Devonshire, which has been employed in several local churches, and the Kentish Rag, which is quarried at several places along the outcrop of the Lower Greensand, there are no limestones worthy of notice employed in Britain for building purposes from the Cretaceous and Tertiary Systems, though they are largely employed in France and other foreign countries. Indeed, it is to tertiary limestones that Brussels and Paris owe much of their architectural beauty; while the nummulitic beds have been used along their course as an available building-stone from the time of the Great Pyramid down to the present day.

II. STONES FOR DECORATION AND SCULPTURE.

Under this head we embrace such stones as are susceptible of a fine polish, and which are employed more for internal decoration and sculpture than for external buildings. It is true that many buildings are exteriorly ornamented with carvings and sculptures, but most of the stones used for interior decorations-alabasters, marbles, serpentines, &c.— would fare badly if exposed to the weather of a severe and variable climate. It is to those more exclusively devoted to ornamentation, therefore, that we devote the present section; and first of the pyrogenous rocks.

The Granites, Porphyries, Basalts, &c.

Of recent years the Granites have come largely into use for external and internal pillars and pilasters, for mantelpieces, pedestals, vases, drinking fountains, graveyard monuments, and sarcophagi. This adoption has arisen partly from their sparkle and beauty, and the high polish of which they are susceptible, partly from their great durability, and partly also from the invention of mechanical appliances by which such hard substances can be expeditiously and cheaply prepared. The granites of Aberdeen (Rubislaw, Stirling Hill, and Cairngall), of Mull, Dalbeattie, Shap, Dartmore, Wicklow, and Galway, are amongst the most esteemed varieties; and there is scarcely a public building in any of our large towns, a first-class mansion-house, or fashionable cemetery, in which they may not be witnessed. It is needless to point to examples where the

use is so frequent, and where year after year it is becoming more general as the wealth of the country increases, and as more effective machinery is invented for raising, cutting, and polishing the material. Having various shades of colour, various sizes of grain, and being capable of being raised in blocks of any dimensions (as already noticed under Building-Stones), the British Granites afford great variety of choice, from the warmer tints suitable to a banqueting-hall, to the sombre and colder hues more appropriate to the monumental obelisk.

The Porphyries, for the reasons stated in the preceding section, are very seldom employed in the United Kingdom for decorative purposes. This is not for want of beautiful tints or susceptibility to polish, but chiefly from their fissured and fractured structure, which renders them incapable of being raised in suitable blocks. Notwithstanding this drawback, they are occasionally used for smaller pedestals, vases, and the like, and several of them produce very fine effects. Indeed, were proper attention paid to the porphyries, some of the Cornish and Scotch varieties would, for internal decoration, compete successfully with the granites. In Scotland several of the porphyries, syenites, and syenitic greenstones are dressed and polished for curling-stones, on some varieties of which (Ailsa Craig and Blairgowrie, for example) connoisseurs set an especial value.

The finer-grained Basalts, though successfully carved in ancient India and the East, are seldom, if ever, attempted in Britain; and yet their dark colours, dull surface, and known durability, render them specially suitable for some kinds of ornamentation. Of the trap-rocks, few, indeed, are suitable for decorative or sculptural purposes; and yet we have seen very handsome vases and minor ornaments fashioned of the variolitic amygdaloid of Glenfarg in Perthshire, and of the black-spotted olive-green variety of Hallyards in Fifeshire.

Slates and Serpentines.

The Slates, though they can be raised in slabs of any size, and cut into any form, are not susceptible of a high polish, and consequently are not used for decorative purposes, save when japanned or enamelled. In this state they are now extensively employed for chimney-pieces and table-slabs; and very fair imitations of marbles (especially black), serpentines, and porphyries can be produced at a much smaller cost than the real materials. Being harder and tougher, the slates can