On Sal Nitrinn and Nitro- Aerial Spirit 119 



in fiery motion, agitate with their own velocity very 

 many others, and these in their turn others of the 

 same mass ; so that indeed the smallest spark is 

 sufficient to cause a wide conflagration, which, yet, is 

 entirely contrary to the ordinary laws of nature. For in 

 other cases when one body in motion impels and moves 

 another at rest, the motion in both is diminished. 

 For a moving body which strikes another body and 

 moves it from its place, loses as much of its own 

 motion as it communicates to the other ; so that 

 when a few particles set in motion a large number of 

 the same mass, the motion in each will be greatly 

 •diminished. 



That the burning particles in fire, then, should in- 

 -crease their motions to such an extent, it seems to me 

 necessary that some other moving body should be 

 added to the ignited particles, to promote and intensify 

 their motion. And I think this is how it occurs. It 

 is no doubt probable that sulphureous particles when 

 divided most minutely, and violently agitated by the 

 application of fire or in any other way, impinge upon 

 the nitro-aerial particles residing in the particles of the 

 air, or of common nitre, and drive them into those 

 small spaces in which the subtle matter revolves with 

 swiftest motion (as we showed above), but that the 

 nitro-aerial and sulphureous particles, when driven 

 within the spherules which are described by that re- 

 volving matter, are driven further and forced out by it 

 with their motions greatly increased, and that at last 

 the nitro-aerial particles, on being violently sundered 

 in this way from the fixed salt of nitre, or from the 

 aerial particles with which they were previously most 

 firmly united, are thrown into a truly fiery motion. 

 Assuredly we must suppose that the sulphureous and 

 nitro-aerial particles, and also the subtle matter, are 



