EXAMPLES 409 



AET. 117. HYDRAULIC MINING. 



The fact that a high velocity jet of water carries an immense amount 

 of destructive energy, was first taken advantage of to any large extent on 

 the Pacific Coast of North America. Here, owing to the configuration 

 of the country, the only available water supply is to be found in com- 

 paratively small streams, at considerable elevations. The construction 

 of a small dam and a flume or ditch to bring the supply to the nearest 

 suitable point on the mountain side, and the further construction of a 

 pipe line leading the supply under pressure down the mountain side, 

 renders available a comparatively small quantity of water under great 

 pressure. In the process known as Hydraulicing, chiefly applied to gold 

 mining, this supply is led into a pressure box securely bolted to the 

 ground at a distance of from 100 to 200 feet from the face of the cliff 

 to be mined. From the pressure box one or two jets, of diameters 

 ranging from 4 inches to 11 inches are led by means of nozzles mounted 

 on ball-and-socket joints, and are played on to the face of the cliff, the 

 debris being carried away by sluices on which the process of washing 

 and amalgamating is completed. 



EXAMPLES. 



(1) A horizontal jet issuing from an orifice 1 inch in diameter dis- 

 charges 2 gallons per second and impinges normally on a large fixed 

 plane. Determine the force exerted on the plane and also, neglecting 

 losses, the maximum pressure intensity likely to be attained. 



>-5 Ibs. 



Answer. .---- 



>'25 Ibs. per square inch. 



(2) If the above plate has edges curved so as to deflect the stream 

 through a total angle of 150, determine the pressure on the plate. 



Answer. 68 Ibs. 



(3) A jet from a rectangular orifice 6" wide X 1" deep impinges on a 

 curved vane 6" wide, with a velocity of 60 feet per second. On incidence 

 the jet makes an angle of 30 with the plane of the vane, and the portions 

 into which it is divided are deflected through total angles of 120 (the 

 smaller portion) and 90 (the larger portion). Determine the pressure 

 on the plane in the direction of the jet. 



Answer. 300 Ibs. 



(4) Assuming a series of vanes similar to that in question (3) to move 



