18 



HYDRAULICS. 



mine, from the bottom of which it is 

 necessary to raise the water standing 



fiff 



at the level bb. cc 1 is the surface of 

 the ground at the top of the well or 

 shaft, at which the discharged water 

 must have an opportunity of escaping, 

 either by running to waste or being con- 

 verted to some useful purpose ; and d is 

 the spring or other elevated source from 

 whence the supply of water for working 

 the machine may be obtained. The 

 machine itself consists of three cisterns, 

 chests, or reservoirs, two of which at 

 e and/ must be made very strong, and 

 perfectly air-tight, while the third at d 

 may be weaker and open at the top, as 

 it is merely for collecting and retaining 

 the spring, rain, or other water for 

 working the machine. The lowest close 

 chest or reservoir e must be sunk be- 

 low the surface bb of the water in the 

 shaft or well a, but must not come into 

 contact with its bottom, otherwise the 

 water would be prevented entering the 

 chest by the valve g, which opens in- 

 wards for its admission. An open pipe 



h h passes from very near the bottom 

 of this chest, through its top, in an air- 

 tight manner, and proceeds upwards in 

 the shaft as far as the surface of the 

 ground, where it bends over to deliver 

 its water as at h c. Another open pipe 

 i i, which may be of rather smaller 

 dimensions than the last, proceeds from 

 the top of the lower chest e to very 

 near the top of the second chest/; and 

 a third pipe, k I, of the same capacity 

 as the iirst, proceeds from very near the 

 bottom of the second close chest, up to 

 the bottom of the high reservoir d, but 

 has a cock or valve at I, by which it 

 can occasionally be shut or opened. A 

 cock or valve, of large dimensions, is 

 also fixed at m, by which the second 

 chest/ can be emptied of its water, and 

 a smaller cock is fixed higher up as at 

 n for discharging its air. To set the 

 machine in action nothing more is ne- 

 cessary than to shut the cocks I and ?n, 

 and open the cock n, from which the 

 air previously contained in the lower 

 chest will escape, and its place will be 

 filled up by the water b b, which will 

 pass through the valve g, until the 

 chest e is completely filled. That done, 

 the air cock n is to be shut, and the 

 water cock / opened, when a column of 

 water, equal to the full height and pres- 

 sure of the cistern d, will rush down 

 the pipe k I, and by filling the chest/ 

 will expel its air, which has no other 

 opportunity of escaping but by the open 

 pipe i i, down which it will pass, and 

 produce a pressure on the surface of the 

 water in the lower chest, equal to the 

 entire height of the column k /; and 

 the air thus thrown into the chest e, 

 being in a condensed state, will force 

 the water previously in that chest up 

 the pipe h h, from whence it will be 

 discharged at c. The lower chest e 

 will now be filled with air, while the 

 upper chest / will be occupied by water: 

 therefore, the cock / must be shut, and 

 that at m opened, when the whole of 

 the water from / will be discharged at 

 c', and will give the air in e an oppor- 

 tunity of returning again into / through 

 the pipe i i ; and as the air from e es- 

 capes, its place will be occupied by a 

 new charge of water, which will rise 

 through the valve g, and again fill the 

 lower chest e, and prepare it for a 

 second discharge. All, therefore, that 

 is necessary to keep the machine in ac- 

 tion is to open the cocks / and m al- 

 ternately, that is to say, to keep the 

 cock / open as long as any water flows 



