After the wood--generally elm--for the shell of the block is cut into proper sizes by circular-saws, its complete formation, including the pin and the sheave, is effected by means of several different machines, all contrived with the greatest mechanical skill, and put in motion by a steam-engine. The first process is that of the boring-machine, which, by means of a centre-bit, pierces a hole to receive the pin, and at the same time, according as the block is intended to be single or double, forms one or two similar holes, at right angles to the former, to receive the first stroke of the chisel which cuts out the space for the sheave. By the second, called the mortising-machine, this space is cut out by a chisel acting vertically, and making about a hundred and twenty strokes a minute, and under which the block is caused to move gradually, so that at each stroke a thin piece of the wood is cut away. After this the block is taken to a circular-saw, which cuts off the corners, and reduces it to the form of an octagon. The shaping-machine, to which it is next taken, consists of two equal and parallel wheels moving on the same axis, to which one of them is permanently fixed, while the other is moveable in the line of the axis, so that, by sliding it nearer to the former, or more apart, as may be required, the shells of blocks of all sizes may be fixed between their two parallel rims. Ten shells of the same size being firmly fixed at regular intervals between those rims, the wheels are put into motion with extreme velocity, and the shells are rounded by striking against a cutting instrument, which at the same time moves in such a manner as to give to each block its proper shape and curvature. When one half of the side has thus been finished, the motion of the wheels is reversed, and the other half finished in the same manner. When one side has been rounded, the shells are reversed, and the other side completed as above. The last process which the shell undergoes consists in scooping out the groove for the strap, or "strop," as the rope is called, which goes round the block. The shell is now completed, and the visitor is next shown the different processes in forming the sheave and the pin.