vi The Preface. 



making a more particular inquiry into 

 the nature of the Air, and to dif cover, 

 if poffble, wherein its great importance 

 to the life and fupport of Vegetables 

 might cojififl ; on which account I was 

 obliged to delay the Publication of the 

 reft of thefe Experiments, which were 

 read two years jince before the Royal So- 

 ciety, till I had made fome progrefs in 

 this i?iquiry : An account of which I 

 have given in the fixth chapter. 



Where it appears by many chymio- 

 fiatical Experiments, that there is dif- 

 fufed thro all itatural mutually attract- 

 ing bodies, a large proportion of parti- 

 cles, which, as the firjl great Author of 

 this important difcovery. Sir Ifaac 

 Newton, obferves, are capable of being 

 thrown off from denfe bodies by heat or 

 fermentation into a vigoroufly elaflick 

 and permanently repelling fate ; and 

 alfo of returning by fermentation, and 



fome- 



