Mr. Cavendish's Experiments on Air^ 370 



be tried was then Introduced by i"fteans of afmali tube, fuch as 

 is ufed for thermometer?, ber.t in the manner reprefented by 

 ABC (fig. 2.) the bent end of which, after being previoufly 

 filled with quickfilver, was introduced, as in the figure, under 

 the glafs D£F, inverted into water, and filled with the proper 

 kind of air, the end C of the tube being kept flopped by the 

 finger ; then, on removing the finger from C, the quickfilver 

 in the tube defcended in the leg BC, and its place was iupplied 

 with air from the glafs DEF. Having thus got the proper 

 quantity of air into the tube ABC, it was held with the end C 

 uppermofl:, and flopped with the finger; and the end A, made 

 fmaller for that purpoie, being introduced into one end of the 

 bent tube M, (fig, i .) the air, on removing the finger fi'om C, 

 was forced into that tube by the prefilire of the quickfilver in 

 the leg BC. By thefe means I was enabled to introduce the 

 exa£t quantity I pleafed of any kind of air into the tube M ; 

 and, by the fame means, I could let up any quantity of loap- 

 lees,or any other liquor which I wanted to^be in contadl with 

 the air. 



In one cafe, however, in which I wanted to introduce air 

 into the tube many times in the fame experiment, I ufed the 

 apparatus reprefented in fig. 3. confifting of a tube AB of a 

 fmall bore, a ball C, and a tube DE of a larger bore. This 

 apparatus was firfl filled with quickfilver; and then the ball 

 C, and the tube AB, were filled with air, by introducing the 

 end A under a glafs inverted into w^ater, which contained the 

 proper kind of air, and drawing out the quickfilver from the 

 leg ED by a fyphon. After being thus furniflied with air, the 

 apparatus was weighed, and the end A introduced into one end 

 of the tube M, and kept there during the experiment ; the 

 way of forcing air out of this apparatus into the tube being by 



thrufting 



