which are fixed between the columns.  The extremity, v, of the axle of the pulley to the right is threaded, and actuates a helicoidal wheel, E, which transmits motion to the wheel, R, through the intermedium of the vertical shaft, F. This transmission, completed by the wheels, R R, and the pitch-chains, G G, is designed to move the saw vertically, through the simultaneous shifting of the carriages, C C. A tension weight, P, through the intermedium of pulleys, D_{1} D_{1}, permits of keeping the saw taut.  A reservoir, H, at the upper part of the frame, B B, contains the water and sand necessary for sawing.  The feeding is effected by means of a rubber tube, I, terminating in a flattened rose, J, which is situated over the aperture made by the saw.  A small pump, L. over the reservoir takes water from K, and raises it to H. The sand is put in by hand.

Above the basin, K, a system of rails and ties supports the carriage, Q, upon which is placed the block of stone to be sawn.  When one operation has been finished, and it is desired to begin another, it is necessary to raise the pulley-carriers and the saw.  In order to do this quickly, there is provided a special transmission, M, which is actuated by hand, through a winch.

The work done by this saw is effected more rapidly than by the ordinary processes, and certain very hard rocks, usually regarded as almost intractable, can be sawed at the rate of from one to one and a half inches per hour.

[Illustration:  FIG. 4.—­APPARATUS FOR SAWING STONE INTO SLABS.]

For sawing marble into slabs of all thicknesses, the arrangement described above may be replaced by a system consisting of two drums having several channels to receive as many saws, or two corresponding series of channeled pulleys, b b (Fig. 4), independent of each other, but keyed to the same axles, i i.  When the pulleys have been properly spaced by means of keys, the whole affair is rendered solid by a bolt, g.  The extremity of the axles forms a nut into which pass vertical screws, c c.  These latter are connected above with cone-wheels, l l, which, gearing with bevel wheels keyed to the shafts, e, secure a complete interdependence of the whole.  The ascending motion, which is controlled by the endless screws, f, and the helicoidal wheels, m, is in this way effected with great regularity.  Uprights, a a, of double T-iron, fixed to joists, k k, and connected and braced by pieces, d d, form a strong frame.

[Illustration:  FIG. 5.—­APPLICATION OF GAY’S STONE SAW IN A MARBLE QUARRY.]

The power necessary to run this kind of saw is less than n x 1/4 H.P., on account of the number of passive parts.  The most interesting application of the helicoidal saw is in the exploitation of quarries.  Fig. 5 represents a Belgian marble quarry which is being worked by Mr. Gay’s method.

Tubular Perforators.—­Mr. Gay has rendered his saw completer by the invention of a tubular perforator for drilling the preliminary well.  It is based upon the same principle as the Leschot rotary drill, but differs from that in its extremity being simply of tempered steel instead of being set with black diamonds.  A special product, called metallic agglomerate, is used instead of sand for hastening the work.