[ 368 ] 



for iiiftance, if in the time of each ftroke, a cubic inch of 

 air intrudes, and the contents of the rec' and cyl' be fifty- 

 cubic inches each ; then the refiduum in the rec' after the 

 firft flroke, would be -k an inch ; to which would be added 

 one cubic inch next admitted ; and by the fubfequent ftroke, 

 half the fum of thefe would be extracSted ; i. e. the half of 

 12^ inches (or f of an inch) which the next addition would 

 encreafe to i^: fo that fuppofing the rec' at firft empty, yet 

 fome would accumulate in every ftroke, until the refiduum 

 would be equal to that intruding during one ftroke, viz. until 

 both would be equal to two inches ; after which one inch 

 would intrude, and one be extradled at every ftroke : fo that 

 the air in the rec' could never be rarefied beyond fifty times, 

 nor finally lefs than to that degree. 



And if the cyV were twice as large as the rec' with its 

 dudls ; the rec' remaining as before ; and the fame quantity 

 (one cubic inch) admitted at each ftroke ; then almoft -^ of 

 this would be drawn into the cyl' by the laft ftroke, and ^ 

 remain in the rec', when the pifton was raifed to the top ; fo 

 that now the greateft rarefadlion would be doubled, and equal 

 to one hundred, which, when the rec' and cyl' were equal 

 was fifty. 



And univerfally, as the capacity of the cyl' is to that of 

 the rec', fo is the whole intruded air during one ftroke, to the 



laft 



