[ 3Si 3 



it \vould not be a perfedl remedy, even though I were mif- 

 Caken in the apprehenfion that fuch abundance of oil, would 

 generate a greater quantity of fadlitious air : for when the 

 valve or dufl in the pll"!on is open, the oil muft defcend 

 through it with all the impurities that may be in it ; and if 

 the oil above the upper valve can defcend into the barrel, the 

 impurities in it will be added, which if they adhered to the 

 ftopple or valve in the plfton, would be likely to occafion its 

 admitting air; alfo the oil being thus churned in the barrel, 

 would perhaps entangle air, efpecially when vifcid, as it will 

 become by corroding the brafs. In this pump, it is not ne- 

 cefTary to ufe oil, efpecially if the barrel be made of pewter; 

 for then the hog's-lard or ointment ufed will not lofe its lu- 

 bricity ; in faft fluid oil is inadmiflible, for it would certainly 

 render the cock, though formed and ground with care (how 

 much more then a valve ?) not air-tight ; the air forcing a 

 paflage even through the oil within the joint, if this be not 

 very clofe, which in a cock whofe key is in continual mo- 

 tion cannot always be ; nor is this hard to conceive ; for where 

 ever a column of mere' as high as that in the baronV, refling 

 over a joint or chafm, could force a pafTage, the air will do 

 the fame, and perhaps more powerfully. 



It will appear then that there is no kind of limitation In 

 the pump here defcribed, which is not in any other ; for in 



the 



