STONE, BUILDING (BuILDINO-STONE, ante). The great merits of a stone for building purposes are easy working. long lasting, equality in color and structure, strength, and, not least important, cheapness. We have in this country almost unlimited supplies of excellen4 stone of every kind; but we are not really a stone-building race for two reasons—exorbitant freights and expensive labor. The divisions of stone from this point of view arc not those of the science of petrography, owing to the methods of cut ting and laying,. Stones are laid in a wall sometimes roughly just as found, only taking care to get a plumb face; this is rubble-work. Again, they may be laid in lines depend= ink on the thickness of the stone, hut with butt-joints unequally distributed—coursing; or the courses may be leveled up only at every three or five rows, the joints between not necessarily vertical—random-coursing; or the stone is laid in courses of blocks, butt joints at stated intervals—ashlar. The strength and the life of a stone depend upon its being laid upon its bed (the strata in a quarry are not always parallel with the horizon), and its having a level, true surface for pressure both received and distributed. It is, then, of great moment to the workman whether the stone can be separated parallel to the.
bed—splittag,e; and also at right angles to it—cleavage. He divides, then, his material .into freestones which split and cleave (gneiss and some trap also); shoes which split (also basalts and some gritstones); limestones which cleave (some granites as well); tough stones which neither split nor cleave—granites and conglomerates (but here belong chalks, though so soft as to be good, in our climate, for inside carving only). The best construc tion has always been done in the hardest stone, and it is necessary to see how such an intractable material is reduced to shape. The workman knows two distinctions—of country-stone and quarry-stone. But the first, often occurring in boulders, is likely to be one of the toughest of all, though usually they are the easily reached outcrops of strata which are more likely to be sandstone or limestone. All quarries are poor and mottled in the top-beds, but the stone becomes better as it descends; also, more beds and of dif ferent thicknesses are struck, the only stones not lying in beds being chalk, conglomer ates, and some granites, though even the latter have at intervals a definite line of split. The three heaviest tools in use are the hammer. the axe, and the pick. The block being reduced to a nearly rectangular shape, the Edges are got to line with the axe, and a broad level edge of the width of a tool, called a draft, is put all around the face of the stone and brought true by the square and the level. The bossed, rectangular panel so
formed may be left quarry-faced, picked, axed, or hammered; the last being a level sur face pitted with small holes if made by the bush-bammer, or scored with parallel lines if made by the patent-hammer. This is the slow process of reducing to shape the tough stones. Moldings and ornaments are roughed out with the pitching tool, a pointed chisel; with the mash-point, a chisel with one level; and finished with drafting and bev eled chisels and tools of the necessary shapes and curves. The work is finally rubbed and polished, with emery and pumice-stone, if desired. This process is evidently much shortened when machinery is used. The saw for marbles is a plain strip of iron fed with sand; that for harder stones is of copper fed with emery. Freestones are cut with a grub-saw having coarse teeth at intervals; and chalk-stones with a heavy band-saw with hooked teeth. Heavy stones are polished by power-rubbers, and manageable ones by themselves, being revolved over a large rubbing-table. Freestones and Ernes:ones can be planed by machinery, also turned; but no machine has yet succeeded in planing gran ite, though balusters have been roughly turned, or rather chipped to shape. The quali ties of a building-stone to be tabulated are its color, strength, weight, absorption, and place of pioduction, together with any peculiarities. The figures which follow are mostly due to the report of gen. Gillmore on the " Building-stones of the United States," 1876. Some fozeign ones general use are included.
Red, purple, and green slate are found on lake Champlain and in Vermont; black and deep purple in Yew Jersey and Pennsylvania: tine colored marbles are found near lake Champlain and the St. Lawrence river, in West Virginia, in and in Cali fornia. In the above table all crushing strength is taken on tho bed. When that taken on edge is greater—very rarely—it shows a 'formation like that of a giwiss. A heavy stone, of high crushing strength and no absorption, is sure to be a good building-stone, unless it contain iron. If not homogeneous, like the Chaumont limestone, usually called a granite, which shows shells when rubbed, it should ne.v:• be morn than tine worked. All stones are bettered by a certain exposure before laying—a weathering; and for sandstones it is indispensable. Chalks, which harden by exposure, can be cut with a light mallet when built in the wall.