CHAP. II. 



' I >H E next qualification requifite 

 J in the corpufcles of Volatile 

 bodies is., that they be not too folid 

 or heavy. For if they be fo^ though 

 their bulk be very fmall, yet 5 unlefs 

 other Circutnftances do much com- 

 penfate their weighty 'twill be very 

 difficult to elevate them, becaufe of 

 the great difproportipn of their fpe- 

 cific gravity to that of the Air 3 

 (which contributes to fuftain and e- 

 ven raife many forts of volatile parts) 

 •and ft?, the ftrength of the igneous 

 effluvia or other agents that would 

 carry them up. Thus we fee, that 

 -filings of Lead or Iron 3 and even 

 Minium (which is the calx of Lead) 

 though the grains they cpnfift of be 

 very finally will not eafily be blown 

 up^ike common duft., or meal, or or 

 ther powders made of lefs ponderous 

 materials. 



i\. third Qualification to be defired 

 fa" the 4 corpufcles that Ihould make 



up 



