LIFTING PUMP. 



Fig. 5. 



ascend, the ascending part of the rope being then longer than the 

 descending, this preponderance gradually decreases until the 

 ascending meets the descending barrel. At this point, the ascend- 

 ing and descending parts of the rope being equal, balance each 

 other, and after this the descending part, preponderating, aids the 

 power just as much as the ascending part previously opposed it. 

 There is, therefore, so far as relates to the weight of the rope, a 

 perfect compensation. 



The same apparatus is much used in France, in raising stone 

 through vertical shafts from subterranean quarries, and other 

 mining operations. 



7. If, instead of a rope and bucket, a pipe or tube be let down 

 into the well, and in this pipe a piston be provided, having a valve 

 in it opening upwards, this piston being worked in the usual 

 manner upwards and downwards, the water would be lifted in the 

 pipe. Such an apparatus is called a lifting-pump, and is repre- 

 sented in fig. 5 : w is the water, c d the piston, u the valve in it 

 which opens upwards. When the piston is moved downwards, 

 this valve opens, and the water passes 



through it. When the piston is moved 

 upwards, the column of water is pushed 

 up, and the valve is kept closed by the 

 pressure of the water upon it. A valve 

 x is placed at c D in a fixed position, 

 through which the column of water 

 passes when the piston rises, and which 

 prevents the return of such water down- 

 wards, the valve being kept closed by 

 the weight of the water above it. The 

 column of water driven upwards by the 

 piston is pushed to any required height, 

 through the pipe E r. In such an ap- 

 paratus, the moving power must be equal 

 to the weight of the water raised, 

 together with the weight of the pump-rod 

 and frame by which the piston is worked, 

 as well as the friction of the moving 

 parts. 



8. A very ingenious form of pump which, though differing 

 altogether in appearance from the lifting pump, acts nevertheless 

 upon precisely the same principle, is shown in fig. 6. It has the 

 advantage of being nearly free from friction, and of being capable 

 of being worked by the weight of an animal walking up an inclined 

 plane, which is the most advantageous manner in which animal 

 power can be applied. 



181 



