Stone is first of building-materials in order and in rank. But there are many varieties and many qualities, from green jasper and peach-blossom marble to such a stone as the spiteful bishop dreaded for his tomb, -

"Stone-Gritstone, a-crumble! clammy squares which sweat As if the corpse they keep were oozing through!"

The principal varieties may be roughly classified as granites, marbles, lime-stones, and sandstones. Other kinds of stone, such as slates, flints, and various igneous rocks, are also used in the construction of walls, but chiefly in the immediate neighbourhood of the quarry or pit where they are obtained.

The use of granite and other igneous rocks in buildings, except in the neigbhourhood of the quarries, is almost invariably restricted to ornamental features. The best granites are extremely hard, non-absorbent, and durable. In consequence of their hardness and the remoteness of the quarries, the cost of polished granite in our towns is invariably high. One disadvantage of the material is its cracking and crumbling away under heat Marbles, like granites, are chiefly used for ornamental purposes. They are hard, crystalline limestones, often beautifully figured, and capable of taking a high polish. The best varieties are too expensive for general purposes of construction, and, as in the case of igneous rocks, the other kinds are seldom used far from the quarries.

Limestones are an important class. The best-known varieties are "Bath stone" and Portland stone, the former (speaking generally) being quite unsuitable for outdoor use in the smoky air of towns, while the best beds of the latter have withstood the atmosphere of London with remarkable success. To some persons, the peculiar blackness and whiteness so characteristic of Portland stone buildings - for example, St. Paul's - are objectionable, but after all, these are Utter than the all-pervading Stygian blackness of sandstone as exemplified in our northern towns, say in the town-halls of Leeds, Halifax, and Manchester.

Other well-known oolitic limestones are obtained from Doulting (Somersetshire), Painswick (Gloucestershire), and Ancaster (Lincolnshire), and a hard and most durable carboniferous limestone is quarried at Hopton Wood, near Wirks-worth, in Derbyshire. Magnesian limestones occur at Mansfield in Nottinghamshire. Anton in S. Yorkshire, and Bolsover Moor, near Chesterfield, in Derby-shire.

The sandstones used in building are obtained chiefly from the Triassic, Permian, and Carboniferons formations. The Triassic rocks are frequently of a red colour, and are not noted for durability; they are quarried in Shropshire, Staffordshire, Cheshire, and some other counties.

Many of the Permian sandstones are also red, such as those quarried in the neighbourhood of Penrith, and at Corsehill and Lockerbie in Dumfries. Some of the English stones of this formation have not the best of reputations, and architects will watch with interest the behaviour of the Cumberland stone used by Mr. Basil Champneys in the Rylands Library recently built in the very midst of Manchester.

Undoubtedly the b«st sandstones come from the Carboniferous group. Gloucester, Yorkshire, Lancashire, Durham, Northumberland, and Edinburgh, are counties well known for their carboniferous sandstones. The stone in this group varies greatly, from the coarsest millstone grit to the finest freestone and flagstone, but the freestone obtained from the well-known quarries near Bristol and in the West Riding of Yorkshire, and at Craigleith near Edinburgh, is close-grained, hard, and extremely durable; such stone is better able to withstand the smoky and acidulated air of towns than any limestone, and has the advantage of being more fire-resisting.

It is impossible in the space at my disposal to say more about the different kinds of building-stone, but one important point affecting the durability of stones and their suitability for the walls of houses must be mentioned. I mean their capacity for absorbing water. An absorbent stone is more likely to decay than one less absorbent, and will also render a house more damp and cold. In the Appendix a table will be found giving the total absorption and the rate of absorption (a most important point) of various limestones and sandstones. It will be noticed that, speaking broadly, the limestones absorb a greater percentage of water than the sandstones, and also absorb it more quickly. The Weldon oolitic limestone in one second absorbs practically its full quantity of water.

A quick rate of absorption shows that every shower of rain must penetrate far into the stone, and so materially add to the dampness and coldness of the wall in which it is used. On the other hand, stones possessing a slow rate of absorption are scarcely affected by a passing shower, and only long-continued rain can render the walls built of them damp.