on which it frequently falls and breaks them to pieces. The operation of taking down large blocks from a great height is very tedious, and is often attended with much danger, as the stone, when it falls on the bottom of the quarries, makes the shivers among which it alights fly in all directions with a force which nothing can withstand. [21] The _plug_ (fig. 12, _c_ _c′_), and _feathers_ (fig. 12, _d_ _d′_), are flat pieces of malleable iron, slightly tapered, and forming together a kind of compound wedge, the two feathers being first inserted into the hole, and the plug being driven between them by a series of gentle blows, from malls of the weight of from 30 lb. to 35 lb. An opening being made in the manner above described, by getting one piece brought down, the same process is continued by cutting off and taking down pieces of eight or ten tons weight, until there be as many blocks in the floor of the quarry as can be easily managed at one time. Those masses are then arranged by means of the crane in convenient positions for being cut up into blocks of the requisite sizes; and as all of them are within range of the crane, they can with its assistance be easily turned over or set in any position. While some of the men are employed in cutting up those blocks, others are clearing away the rubbish, and others are boring holes or making ready for a fresh blast. [Illustration: No. 13.] If those blocks, which we have supposed to be brought down to the quarry floor and to be ready for cutting, exceed seven feet in depth of cut, their farther subdivision will require the use of the plugs and feathers already described; but if their depth or thickness fall short of that, the ordinary iron wedges will answer. If the cut be of the depth of about 6 feet, the wedges must be placed about 3 inches apart from side to side; but if the depth of cut be less, they may be set 4 or 5 inches asunder. The method of setting in those wedges is as follows:--The person who cuts the wedge-holes generally works in a sitting posture, and if the block will admit of it, he prefers to bestride it, with a stone, as a stool, under each foot. He works with a pick of 16 lb. weight, having a handle only 16 inches long, with which he cuts the first hole generally about 3 inches from the end of the block. The holes are for the most part about 2¹⁄₂ inches deep, and 3¹⁄₂ inches long, and must be well cleared out at the bottom with a sharp pick; and the wedges must be set in a line as fair and straight as possible. Cutting wedges of that kind are of iron, from 7 to 9 inches long, and 2¹⁄₂ inches broad, and weigh about 7 lb. weight each. When in good order they must not be sharp in the mouth, but about ³⁄₈ of an inch thick, to prevent their _grounding_ in the bottom of the hole; for if they but touch the bottom of the hole, they fly out at the first touch of the mall. When the wedges have been all properly arranged for