858 



HYDRAULIC MACHINERY, FOR MINES 



natural falls have been extended by Sir William Armstrong in the following 

 manner : 



When the moving power consists of a natural column of water, the pressure 

 rarely exceeds 250 or 300 feet ; and in such cases he has employed, to produce rotary 

 motion, a pair of cylinders and pistons, with slide-valves resembling in some degree 

 those of a high-pressure engine, but having relief valves D to prevent shock at the 

 return of the stroke, as shown in Jig. 1173, page 835. Where the engine is single- 

 acting, with plungers instead of pistons, the relief valves are greatly simplified, and, 

 in fact, are reduced to a single clank in connection with each cylinder, opening 

 against the pressure, which is the same as the relief valve in the valve chest of the 

 hydraulic crane. The water-pressure engine erected at Mr. Beaumont's lead mines, at 

 Allenheads in Northumberland, present examples of such engines applied to natural 

 falls. They were there introduced under the advice of Mr. Sopwith, and are now 

 used for the various purposes of crushing ore, raising materials from the mines, 

 pumping water, giving motion to machinery for washing and separating ore, and 

 driving a saw-mill and the machinery of a workshop. In all these cases nature, 

 assisted by art, has provided the power. Small streams of water, which flowed down 

 the steep slopes of the adjoining hills, have been collected into reservoirs at elevations 

 of about 200 feet, and have been laid from these to the engines. 



1189 



Another application of hydraulic machinery at the same mines has been made where 

 falls of sufficient altitude for working such engines cannot be obtained. For the purpose 

 of draining an extensive mining district and searching for new veins, a drift or level 

 nearly six miles in length was executed. This drift runs beneath the valley of the 

 Allen, nearly in the line of that river, and upon its course three mining establishments 

 were formed. At each of these, power was required for the various purposes above 

 mentioned, and it was desired to obtain this power without resorting to steam-engines. 

 The river Allen was the only resource, but its descent was not sufficiently rapid to 

 permit of its being advantageously applied to water-pressure engines. On the other 

 hand, it abounded with falls suitable for overshot wheels, but these could not be 

 applied to the purposes required without provision for conveying the power to many 

 separate places. Under these circumstances, it was determined to employ the stream 

 through the medium of overshot wheels in forcing water into accumulators, and thus 

 generating a power capable of being transmitted by pipes to the numerous points 

 where its agency was required. 



A somewhat similar plan is also adopted at Portland Harbour, in connection with 



