172 Analyfis of the Air . 
this method is, the fequel of thefc Experi- 
ments will fhew. 
The illuftrious Sir Ifaac Newton (quesy 
31ft of his Optieks) obferves, That <c true 
permanent Air arifes by fermentation or 
ct heat, from thofe bodies which the chy- 
<c mifts call fixed, whofe particles adhere by 
* c a ftrong attraction, and are not therefore 
“ feparated and ratified without fermenta- 
€C tion. Thofe particles receding from one 
another with the greareft repulfive force, 
“ and being moft difficultly brought toge- 
u ther, which upon contad were moil ftrong- 
ly united. And query 30. Dcnfe bodies 
u by fermentation ratify into feveral forts 
of Air ; and this Air by fermentation, and 
u fometimes without it, returns into denfe 
tc bodies/' Of the truth of which we have 
evident proof from many of the following 
Experiments, viz. 
That I might be well affured that no part 
of the new Air which was produced in di- 
ftillation of bodies, arofe either from the 
greatly heated Air in the retorts, or from 
the fubftance of the heated retorts, I firft 
gave a red hot heat both to an empty glafs 
retort, and alfo to an iron retort made of a 
musket barrel ; when all was cold, I found 
the 
