HYDRAU1IC APPARATUS. 
210 
I 
XI. 
Letter from Mr* William Close, giving a Description of 
the Means of causing his hydraulic Apparatus to act with * 
variable Quantity of Water . 
To Mr. Nicholson . 
Dalton, June A, 1813. 
SIR, 
I T has long appeared to me, that the only thing wanting for 
the completion of the hydraulic apparatus, the description 
and drawing of which you have done me the honour to insert 
in the 12th vol. of your Journal, is to make it operate with a 
variable quantity of water. 
This, I conceive, may be done by having several pipes to 
convey air to the bell B. of the apparatus, pi. I. fig. 2, whose 
orifices open at different heights in the cistern, and which are 
supplied with air at some depth below the surface of the wa- 
ter. 
With this view, let each pipe be contracted to half its dia?- 
meter, at about the depth of one foot below the surface of the 
water in the cistern, and then gradually widen to its general 
width, and let several small holes be made in its side, at the 
contracted part. 
Now, when water descends in these pipes, air will enter at 
the small holes, and the operation of the apparatus in raising, 
will be in proportion to the number of pipes in action. 
A circular guard must be fixed on each pipe, at some height 
above the contraction, to prevent any water from coming at the 
air holes. 
I set up an apparatus, such as delineated in fig. 1 j but with j 
the alterations which have been mentioned. The general width 
of the pipe A. B- was three quarters of an inch in diameter, 1 
and about twenty-seven feet long. The other pipe was one I- 
inch in diameter— the fall of water four feet. 
Upon trial, one pint of air descended into the bottle above 
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