PHYSICAL AND LITERARY.95 



" of the attra(5lion of the body, than they 

 *' recede from it, and alfo from one ano- 

 " ther with great ftrength, and keep at a 

 " diftance fo as fometimes to take up above 

 " a million of times more fpace than they 

 *' did before in the form of a denfe body ; 

 *' which vaft contra6lion and expanfion 

 " feem unintelligible by fuppofing the par- 

 " tides of air to be fpringy and ramous 

 ** and rolled up like hoops, or by any o- 

 *' ther means than a repulfive power. The 

 *' particles of fluids which do not cohere 

 " too flrongly, and are of fuch a fmall' 

 " nefs as renders them mod fufceptible 

 *' of thofe agitations which keep liquors 

 " in a fluor, are mod eafily feparated and 

 " rarified into vapour, and, in the Ian- 

 " guage of the chymifls are volatile, rarify- 

 " ing with an eafy heat, and condenllng 

 ** with cold. And becaufe the particles 

 '* of permanent air are grofTer, and arife 

 ** from denier fubflances than thefe of va- 

 ** pour, thence it is that true air is more 

 " ponderous than vapour, and that a 

 " moid atmofphere is lighter than a dry 

 " one, quantity for quantity. From the 



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