[ 35^ ] 



fee the leaft ground for doubt ; and am perfuaded, that fuch 

 faditious air is generated more copioufly, by the moifture, or 

 fomc quality in the atmofpheric air in the reC", in damp wea- 

 ther, than when the air is dry. 



An opinion or rule given without a reafon, rcfts only on the 

 authority of the didator : that this may not reft on mine, I 

 muft beg leave to relate on what it is founded ; for the fad, 

 if it be one, is of the laft confequence to the perfedion of the 

 machine, as indicating a new principle, with refped to which 

 it ought to be conftruded. I muft premife, that in making the 

 following obfervations. I ufed no other rec than a fmall glafs 

 veflel, covering a reduced baromr-gage, whofe capacity, together 

 with that of the duds of the reC (which conftitute a part of 

 the contents of every veffel to be cxhaufted) was only about 

 eight cubic inches ; for the fmaller the recipient is, the greater 

 and more diftinguifliable by the eye, will be the afcent or 

 defcent of the mercV in the gage, on the addition or fubtradion 

 of a given quantity of air. The mercy in the gage being by 

 exhauftion brought down within one inch of the level of that 

 in the ciftern, which was always done, the following efteds 

 were produced in working the pump ; which I noted a great 

 many times to have happened invariably. 



I ft, When 



