I 



Oft Sal Nitrum and Nitro- Aerial Spirit 137 



place deprived of air there are nitro-aerial particles, 

 and that the fire produced there by the solar rays, con- 

 centrated by means of a speculum, consists in this, 

 that the nitro-aerial particles are so much impelled 

 at the point where the solar rays meet that they 

 are thrown into a really fiery motion. So that the 

 medium by whose impulse the rays of light are propa- 

 gated seems clearly to be nothing else than nitro- 

 aerial particles very densely distributed through the 

 atmosphere. Indeed it is probable that nitro-aerial 

 particles when moving in a luminous body with a 

 very rapid and fiery motion, communicate to the 

 other nitro-aerial particles, dispersed through the 

 ether and of the same nature as themselves, the 

 peculiar impulse by which the rays of light are 

 propagated. 



But you will say, if nitro-aerial particles exist in a 

 place void of air, why cannot a lamp be kindled and 

 burn there since no requisite is lacking for the pro- 

 duction of flame. I answer that the sulphureous 

 particles of a lamp contribute in no way to produce 

 flame, except in so far as they strike out from aerial 

 particles, the nitro-aerial particles which, sundered with 

 violence, are thrown into fiery motion, as was pointed 

 out above. But sulphureous matter seems to be by 

 no means fit for throwing into fiery motion the nitro- 

 aerial particles disseminated through the ether. 



Like igneous particles, so also moving particles of all 

 substances whatsoever which give an impulse to the 

 luminous medium in the due way, are capable of pro- 

 ducing light. Hence it is that a kind of feeble light is 

 emitted by the glow-worm, by rotten wood, and the 

 like. 



Further that light is propagated by the impulse of 

 nitro-aerial particles seems to be confirmed by its pass- 



