Chap. 3.] Pump. 455 



its lower extremity. This extremity was plunged 

 into a tun full of water. M. Bellange had made a 

 fmall perforation in this pipe of about one twenty- 

 fourth of an inch diameter, at twelve or fifteen inches 

 above the furface of the water in the tun. The appa- 

 ratus being difpofed of in this manner, he moved the 

 pifton gently, but the water did not rife; the fmall 

 hole furnifhed a fufficient quantity of air to fill the 

 afpiration pipe. He then moved the pifton with great 

 velocity ; the fmall hole could not, in fo fhort a fpace 

 of time, furnifh a fufficient quantity of air to fill the 

 pipe; a little water role and mixed itfelf with the air, 

 fo that the column became compofed of fmall cylin- 

 ders, alternately of air and water, and though it was 

 fifty-five feet high, it was much fhort of the weight 

 of a column of water thirty-two feet high. If we 

 calculate, therefore, according to the diameter of the 

 body of the pump, and the extent in which the pifcon 

 played, what quantity of water this pump would have 

 furniflied if the air had not entered, and then compare 

 this quantity with that which it really furnifhed, we 

 lhall find that the latter is greatly inferior ; for in fix 

 minutes five hundred and thirty ftrokes of the pifton 

 may be given, which would furnifh only thirty-fix 

 pints of water j this pump, therefore, would not fur- 

 nifh the eighth part of the water which it ought to do 

 upon the common principles of the fucking pump; fo 

 that though the conftruction might appear to be more 

 ingenious, it was not in reality to be preferred to that 

 of Seville. 



The compound forcing pump is compofed of the body 



of the pump G H, (Plate VIII. Fig. 2.) open above, 



and the afpiration pipe H V adapted to the lower end. 



At the union of this pipe with the body of the pump 



Gg 4 is 



