* The Author s experiments and ohfervations refpeding the quantity 

 of Air contained in IFater and other Fluids. 



1 HAVE leen an engine in form of a pump, defigned to extract or 

 pump out the air from water, but the operation itfelf I never faw. 

 Since that time, I turned my thoughts to the making forae fmall 

 inftruments for this purpofe, and from which I hoped to derive 

 more fuccefs, than from the pump I had feen in the hands of other 

 perfons. 



For this purpofe, I took fome very round fmooth glafs tubes, 

 and of an equal breadth or bore throughout ; that extremity, how- 

 ever, which feemed (if any) wideil of the two, I prepared for the 

 introduction of a pifton or fucker. 



Plate XX. fg. 1, ABCED, reprefents one of thefe glafs tubes 

 drawn upon a reduced fcale, for the part marked AB, was upwards 

 of fourteen inches long, and B C, twelve ; the cavity or bore was, 

 throughout, nearly the feventh part of an inch in diameter. The 

 cavity in the fmall glafs tube, v\ hich by the flame of a candle I had 

 joined to the larger tube, was one iixth part the fize of that larger 

 one, confequently, the contents of the larger glafs tube would be 

 thirty-fix times the tube C E D : this lall tube, C E D, M^as two 

 inches and two thirds of an inch long. 



I then took a brafs wire, VL^fig. 2, G H I K, at one end of which, 

 with a file, I made three notches, to which end, I faftened a fmall 

 piece of leather, binding it on with fine filk, which filk was very 



* This EfTay, and the next following, though not pertaining to microfcopical fiibjefts, arc 

 infcrted to.fliew the Aufhoi's diligence in his inquiijes, and the accuracy of his obfcrTations 

 in other branches of Natural Philofophy. 



Qq2 



