ATMOSPHERICS L AIR. 73 



ftate on the furface of the water, yet when it was con- 

 denfed, on inverting the tube, during the time that it 

 was pafling the whole length of the tube, as readily as 

 frefh air from the atmofphere. Befides, it requires a 

 confiderable time before the water thus deprived of all 

 air will abibrb that which has been produced, or extri- 

 cated, from it, when the veffel is inclined, and con- 

 fequently the prelTure of the atmofphere removed. 



Alfo, in order to obviate this objection, I kept the 

 extremity of the tube carefully covered with my finger 

 all the time that it was inverted till the moment that the 

 air muft be let out, and mercury put in, fo that it was 

 not expofed to the atmofphere fo much as the tenth of a 

 fecond ; and yet I found repeatedly, that the air was pro- 

 duced as readily as when it had been expofed to the at- 

 mofphere ^^as I fometimes purpofely did it] feveral 

 minutes. 



1 would farther obferve, that, in this procefs, if the 

 veiTel containing the water and mercury be inverted, and 

 a vacuum appear, as it inftantly will, in the form of a 

 bubble, for ever fo fliort a time, a perceivable bubble of 

 permanent air will be produced. I do not therefore fee 

 but that, by means probably of heat, air is producible 

 from the fame water without any limit. 



In order to make any quantity of water as free from 

 'air as poffible, agitation is ncceffary. But when by the 

 frequent repetition of this procefs tlie greateft effeiS has 

 been produced, and the air, or vapour, has remained 

 long upon the water, agitation will diminifli it, part of 

 the newly generated air being imperfectly formed, and 

 more readily imbibed by the water than that which had 

 been a longer time in the ftate of air. This diminution 

 of the bulk of a bubble of air by agitation appears to 

 be the moft certain teft of as perfedl an extrication 

 of air from water as can be attained. Bvit even after 



this 



