[ 36r ] 



been taken ofF) and the air preffed with its whole weight on 

 the top of the pifton, it would be moft likely to force an entrance 

 by this, when there w^as the mofi: perfed: vacuum under it, as 

 in the fecond cafe ; whereas then the mere'' never rofe in the 

 gage, which proved that no air had got under the pifton : and 

 in the other cafes, fincc the gage-rec' was fo fmall in propor- 

 tion to the barrel, and the air in it was thirty times rarefied 

 before the pifton was raifed, and above one hundred and fifty 

 times after it was raifed to the top, it muft have been always 

 fo rare under the pifton as to have favoured the irruption of 

 the air incumbent on it : and if air had been admitted any 

 where but by the pifton or cock, its quantity admitted would 

 be always the fame in a given time, which would contradid 

 the appearances that took place ; however the changes in the 

 gage were computed from the altitude at which it flood juft 

 before the variation. 



And if it ftiould occur, that the afcent of the mere'' in the 

 gage, was caufed by external air adhering to the fides of the 

 barrel, and entangled in the oil or ointment there, which was 

 expofed to the air when the pifton was put down ; a part of 

 which air, not brought up by the afcending pifton as being en- 

 veloped in the oil, yet would expand itfelf into the vacuum 

 under the pifton, and remain there until a paflage was opened 

 for it into the rec' ; we ftiall find this will not agree with the 

 Vol. VI, Z z appearances j 



