Scientific American Supplement, No. 620 | Page 7

_g'_, in the interior of the columns, and the nuts of which are affixed to the sliders, D and D'. To this effect, the shaft, q, is provided at its extremities with endless screws that gear with two wheels, _q_', with helicoidal teeth fixed near the middle of two parallel axes, r, running above the table, B, and terminating in bevel wheels, _r'_, that engage with similar wheels fixed at the end of the screws, g and _g'_.
The car that carries the block to the saw consists of a strong frame, E, mounted upon four wheels. This frame is provided with a pivot and a circular track for the reception of the cast iron platform, E', which rests thereon through the intermedium of rollers. Between the rails, e, and parallel with them, are fixed two strong screws, _e'_, held by supports that raise them to the bottom of the car frame, so that they can be affixed thereto. When once the car is fastened in this way, the screws are revolved by means of winches, and the block is thus made to advance or recede a sufficient distance to make the lines marked on its surface come exactly opposite the saw blade.
In sawing hard stones, it is necessary, as well known, to keep up a flow of water and fine sand upon the blade in order to increase its friction. Upon two platforms, b, at the extremities of the machine, are fixed the water reservoir, C, and the receptacles, C', containing fine sand or dry pulverized grit stone. As may be seen from Figs. 5 and 6, the bottom of the sand box, C', is conical and terminates in a hopper, T, beneath which is adjusted a slide valve, t, connected with a screw that carries a pulley, T'. By means of this valve, the bottom of the hopper may be opened or closed in such a way as to regulate the flow of the sand at will by acting upon the pulley, T', through a chain, _t'_, passing over the guide pulley, _t2_. A rubber tube, u, which starts from the hopper, runs into a metal pipe, U, that descends to the guide, H, with which it is connected by a collar. Under the latter, this pipe terminates in a sphere containing a small aperture to allow the sand to escape upon an inclined board provided with a flange. At the same time, through the rubber tube, c, coming from the reservoir, C, a stream of water is directed upon the board in order to wet the sand.
As the apparatus with but a single endless saw makes but two kerfs at once, Mr. Auguste has devised an arrangement by means of which several blades may be used, and the work thus be expedited.
Without changing the general arrangements, he replaces the pulleys, P and P', by two half drums, V and V' (Figs. 8, 9, and 10), which are each cast in a piece with the crosspieces, D2 and D3, designed to replace D and D', and, like them, sliding up and down the columns, A, of the frame. Motion is transmitted to all the saw blades by a cog wheel, X, keyed to the vertical shaft, f, and gearing with small pinions, x, which are equally distant all around, and which themselves gear with similar pinions forming the radii of a succession of circles concentric with the first. All these pinions are mounted upon axles traversing bronze bearings within the drum, which, to this effect, is provided with slots. The axles of the pinions are prolonged in order to receive rollers, _x'_, surrounded with rubber so as to facilitate, through friction, the motion of all the blades running between them.
The other drum, V', is arranged in the same way, except that it is not cast in a piece with the carriage, D3, but is so adjusted to it that a tension may be exerted upon the blades by means of the screw, d, and its hand wheel.
Through this combination, all the blades are carried along at once in opposite directions and at the same speed.--_Publication Industrielle._
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ROBURITE, THE NEW EXPLOSIVE.
A series of experiments of great interest and vital importance to colliery owners and all those engaged in mining coal has been carried out during the last ten days in the South Yorkshire coal field. The new mines regulation act provides that any explosible used in coal mines shall either be fired in a water cartridge or be of such a nature that it cannot inflame firedamp. This indeed is the problem which has puzzled many able chemists during the last few years, and which Dr. Roth, of Berlin, claims to have solved with his explosive "roburite." We recently gave a detailed account of trials carried out