On Sal Nitruin and Nitro- Aerial Spirit 149 



when the clouds dash violently against one another 

 in this way, the air around is necessarily thrown into 

 a tremulous motion ; and this agitation of the air is 

 conveyed, with scarcely any loss of time, to a great 

 distance, on account of the continuity of the atmo- 

 sphere. Nay, in whatever manner thunderstorms are 

 produced, the air must certainly be agitated with a 

 very great commotion. 



Now I certainly think it is probable that the aerial 

 particles, since they are solid and rigid, strike forcibly 

 against each other in consequence of the violent 

 concussion of the air produced in a thunderstorm, 

 and that they wear themselves by the powerful and 

 sudden mutual shock. The consequence is, that the 

 nitro-aerial particles, struck out from the aerial particles 

 and thrown into a fiery motion, produce a certain light 

 and momentary flame (such as that of lightning is) 

 which extends over nearly the whole hemisphere. 

 For it is very much as though an immense congeries 

 of very small flints were struck with so violent a blow 

 that an almost infinite number of sparks of fire should 

 be struck out from the collision of its innumerable 

 particles ; for in this case a certain light flame, pro- 

 pagated through the whole aggregate of flints, would 

 be suddenly kindled. Besides 1 do not know whether 

 or not the nitro-aerial particles disseminated among 

 the aerial particles (from some sort of impulse of 

 which, I assume that light arises) can be thrown by 

 the violent concussion of the atmosphere into such 

 a motion as is requisite for the production of light. 

 And indeed if lightning were light and nothing 

 more, it would seem to be due sometimes to this 

 cause. 



As to the fervent and very intense sultriness, which 

 often precedes thunderstorms, it must not be thought 



