v The PREFACE. 



Where it appears by many chymio ftatical 

 Experiments, that there is diffufed thro 1 all 

 natural, mutually attracting bodies, a large 

 proportion of particle s 7 wEicb\ as the fir fl great 

 Author of this important difcovery, Sir Ifaac 

 Newton o 'ferves, are capable of being thrown 

 of from denfe bodies by heat or fermentation 

 into a vigor oujly elaftick and permanently re- 

 pelling ft ate : And alfo of returning by fer- 

 mentation and fometimes without it, into 

 denfe bodies ; It is by this amphibious pro- 

 perty of the air, that the main and principal 

 operations of Nature are carried on 5 for a 

 mafs of mutually attracting particles, with- 

 out being blended with a due proportion of 

 elaftick repelling ones, would in many cafes foon 

 co ale fee into aflitggiflo lump. It is by thefe pro- 

 perties of the particles of matter thathefolves 

 the principal Thoenomena of Nature. AndTDr. 

 Preind has from the fame principles given a 

 very ingenious Rationale of the chief opera- 

 tions in Chymiftry. It is therefore of impor- 

 tance to have thefe very operative properties of 

 natural bodies further afcertained by more 

 Experiments and Obfervations : And it is 

 with fat isf action that we fee them more and 

 more confirmed to us, by ever j farther enquiry 



