The connection by means of screw-bolts of an iron radial arm with the iron rim of a wheel is shown in figure 5 (II. 63), and in Figure 7 the con nection of the iron and wooden ventilated paddles with the rim. The purpose of the latter is to permit the escape of the entrained air in the buckets of overshot- and high breast-wheels, and to obtain the fullest effect of the billowing water.
In Figures 6, 8, and 9 is given, in sections, the manner of connecting the iron or steel " pivot " with a hollow cast-iron shaft (fig. 9), one of plate iron 8), and one of wood (fig. 6), the latter showing also the method of securing upon a wooden shaft a cast-iron hub centred with screws.
77ze Pellon lI'ricr-wlied (pl. 64, fig. 1), invented by I,. A. Pelton, occu pies a position between a water-wheel proper and a turbine. This water pressure motor is largely employed in the mining districts of the Pacific coast, where it utilizes the water-power of the mountain streams. The periphery of the wheel, whose shaft rests in bearings on a timber frame work, is set around with metallic buckets, to which the water, under pressure, is directed from a nozzle so set as to deliver the water parallel with the wheel. Each of the buckets has a partition which divides the impinging stream of water, and, being open with a free discharge, the buckets are not obstructed by leaves, roots, etc., nor by ice if the wheel be kept running. In point of efficiency, the highest theoretical results claimed to be due to water-power (35 per cent.) are realized under all heads of fall and every variety of application, while under favoring con ditions it reaches as high as 90 per cent. or 92 per cent.
"One of the most remarkable instances of electrical transmission of power has recently been accomplished on the world-fatuous Comstock Lode, Nelada, and the almost equally famous Sutro Tunnel. At the Nevada Mill there is a ro-foot Pelton water-wheel, which receives water through a pipe-line delivering water from the side of Mount Davidson under a head of 46o feet, giving two hundred horse-power. Here the water is caught up, delivered into two heavy iron pipes, and conducted down the vertical shaft and incline of the Chollar mine to the Sutro Tun nel level, where it is again delivered to six Pelton water-wheels, this time running under a head of 168o feet. Each of the six wheels is but 4o
inches in diamter, weighing 225 pounds, but with a jet of water less than of an inch in diameter they develop one hundred and twenty-five horse power each. On the same shafts, which revolve nine hundred times a minute, are coupled six Brush dynamos, which generate the current for the electric motors that drive the stamps in the mill above ground. The result is that, where it formerly took 312 miners' inches of water to operate thirty-five stamps, but 72 inches are now required to run sixty stamps. This is the most enormous head of water ever used by any wheel, and by itself constitutes an era in hydraulic engineering. A bar of iron thrown forcibly against this tremendous jet rebounds as though it had struck against a solid body instead of a mobile fluid. The speed of this jet, where it impinges against the buckets of the wheel, is two miles per minute, or 176 feet a second." Water applying to a working machine the principle of the force-pump (see p. 328), this transport machine can be converted into a motive machine by simply reversing its action—that is, instead of the delivery-valve being raised and the water pressed into an ascending pipe by the movement of the plunger-piston actuated by a separate motive power, the delivery-valve can be raised by external means and the piston moved to and fro by discharging, after each stroke of the piston and the filling of the cylinder, the contents of the latter by opening the suction valve. The water here appears, not as a transported mass lifted at the expense of motive power, but as a motive substance which subsides with the production of the mechanical effect.
constructed according to the above principle are called " hydraulic " or " water-pressure " engines, in which water under pressure drives a piston in a cylinder somewhat in the manner of steam. They essentially differ, however, from piston-pumps in their mechanism, through which the opening and closing of the valves are automatically effected by the engine itself, as also in appliances which are better adapted to the purpose than pump-valves, and through which the supply and discharge of the water can be regulated.