328
MODERN STEAM PRACTICE.
raising materials from the mines, pumping water, giving motion tomachinery for washing and separating the ores, and driving a saw-mill and the machinery of a workshop. Small streams of water,which flowed down the steep slopes of adjoining hills, have beencollected into reservoirs at elevations of about 200 feet, and pipeshave been laid from them to the engines. Water-pressure machin-ery is invaluable in such a hilly district, where steam power isalmost impracticable in a commercial point of view, from the greatcost of conveying coals to the works.
An application of hydraulic machinery in situations where fallsof sufficient altitude for working water-pressure engines cannotbe obtained has been carried out at these mines, which deservesspecial notice. For the purpose of draining an extensive dis-trict, and searching for new veins, a drift way or open level nearly6 miles in length was cut. This drift way runs beneath thevalley of the Allen, nearly in the line of that river, and uponits course three mining establishments have been erected. Ateach of these power was required for the various purposes alreadymentioned, and it was desirable to obtain this power without re-sorting to steam engines. The river Allen was the only resource,but its descent was not sufficiently rapid to permit of its beingadvantageously applied to water-pressure engines; it abounded,however, with falls suitable for overshot wheels, and it was deter-mined to employ the stream, by means of such wheels, in forcingwater into accumulators, and then transmitting by pipes the powerthus stored to the numerous points where it was required. In thisarrangement intensity of pressure takes the place of magnitude ofvolume, and the power derived from the stream assumes a formsusceptible of unlimited distribution and division, and capable ofbeing utilized by small and compact machines.
A somewhat similar plan is also adopted at the coaling establish-ment for the navy at Portland Harbour . The object in this caseis to provide power for working hydraulic cranes and haulingmachines for coaling war Steamers. A reservoir on an adjoiningheight affords an available head of upwards of 300 feet; but inorder to diminish the size of the pipes, cylinders, and valves con-nected with the machinery, and also to obtain greater rapidity ofaction, a hydraulic pumping engine and accumulator are interposed,so as to intensify the pressure and diminish the volume of wateracting as a medium of transmission.