I 



On Sal NitriLtn and Nitro- Aerial Spirit 17 



think we ought to agree with recent philosophers, 

 who beHeve that fire can be produced by the subtle 

 particles of any kind of matter if they are thrown into 

 violent agitation. In fact, while the Peripatetics 

 formerly assigned a distinct quality for almost every 

 natural operation and multiplied entia unnecessarily, 

 the Neoterics on the other hand maintain that all 

 natural effects result from the same matter, its form 

 and its state of motion or of rest alone being changed, 

 and that consequently any thing whatever may be 

 obtained from any thing. But in truth this new 

 philosophy seems to depart too far from the doctrine 

 of the ancients, and I have thought it better to take 

 an intermediate path. It would certainly be a reason- 

 able supposition that certain particles of matter which 

 are unlike in no other respect than in the form and 

 extremely solid and compact contexture of their parts, 

 differ so much that by no natural power can they be 

 changed one into another, and that the Elements con- 

 sist of primary, and in this way peculiar, particles. 

 Hence, I conceive that fire can be produced only by 

 particles of a certain kind, and this is obvious from 

 the very fact that it cannot be kindled without nitro- 

 aerial particles. 



As regards the sulphureous particles which are 

 also indispensable for the production of fire, the 

 necessity for them seems to arise merely from this 

 that they are naturally fit to throw nitro-aerial 

 particles into a state of rapid and fiery commotion. 

 And I think it is not impossible that fire may be pro- 

 duced without the presence of sulphureous particles. 

 The fire from the solar rays when condensed by a 

 burning-glass, and the other celestial fires appear to 

 be of this sort. For although sulphureous particles 

 are absolutely necessary for kindling the kitchen fire, 



B 



