850 



HYDRAULIC MACHINERY, FOR MINES 



tho perpendicular or, as miners say, at nine o'clock', (2) when the fall exceeds 60 

 feet, a turbine, or water-pressure engine, will generally bo found less costly and more 

 effective ; (3) wheels placed one over tho other, and geared together, so as to employ a 

 high fall of water, do not afford satisfactory results. 



Fig. 1179 illustrates an overshot wheel employed in pumping at tho Laxey Mines, 

 Isle of Man. Tho diameter is 72 feet 6 inches ; width between shroudings, 6 feet ; 

 length of shaft, 17 feet; diameter of shaft, 21 inches; length of crank, 5 feet; stroke, 

 10 feet; stroke in pump, 8 feet. Tho water is convoyed in pipes 2 feet diameter, 

 and, after rising through the column, is carried to tho top of the wheels by means of a 

 launder. On one side of the crank a balance ' bob ' is fixed ; from the other is ex- 

 tended the sweep and ' flat rods,' reaching to the pump shaft, about 200 yards 

 distant. 



At Wheal Friendship, Tavistock, under the direction of the late Mr. Taylor, an 

 aggregate fall of 626 foot was utilised through the medium of seventeen water-wheels, 

 eight of which were employed in pumping. The largest wheel was 51 feet diameter, 

 and 10 feet between the shrouding. The water ran into the buckets at the rate of 



5, 600 gallons per minute, consequently tho horse-power expended was ( : ) 



\ 33,000 / 

 86 . Tho wheel made 5 revolutions per minute ; length of stroke in tho pump, 6 feet ; 



1180 



1181 



effective journey per minute, 30 feet ; weight of water in tho various lifta or columns 

 of pumps, extending a depth of 188 fathoms, 66,415 Ibs. Tho work perfornml l>v 

 this wheel was therefore 69 per cent, of tho power expended, or equal to 60 effectivo 

 horse-power. 



Turbine. The use of turbines in mining operations is somewhat limited by the 

 nigh speed of tho wheels, and the necessity of employing intermediate shafts and 

 wheel-gear. "Without reducing gear, the apparatus cannot bo directly applied either to 



