C 526 1 
collifion of nitrous particles fhould ever happen in 
the common feat of thunder, which is in the moft 
collected fhowers that defcend : For there the nitrous 
particles mult be abforb’d and diflipated in the water; 
in which date I think it impoflible for them to take 
fire. 
Thefe, and many other confiderations, too prolix 
for the compafs of a letter, induced me to fearch for 
fome other caufe of thunder ; which I think I have 
difcover’d in that fire, which is made apparent in 
electrical experiments. This fire pervades and ad- 
heres to mod bodies ; while it flies, and cannot be 
brought to mix with fome particular bodies. I fhall 
here only mention two; air, which it flies and 
lliuns, and water, which it more intimately pervades 
than almod any other body. I mud alfo obferve, 
that this fire does not only pervade bodies, but that 
it furrounds and covers them to a certain didance 
from their fuperficies, in proportion to the date of 
its aClivity, which is increafed by heat : And that, 
when it is artificially or accidentally protruded upon 
any body beyond its natural affeCtion, it will fly oft" 
to the next approaching body, which is not fo much 
impregnated with this fire ; and, when it departs in 
any confiderable quantity, it makes a great noife or 
crack : All which is demondrated by eleCtrical expe- 
riments. Now, to fhew, that this fire is the real 
caufe of thunder, we need only confider it attending 
every vedel of humid vapour rifing into the atmo- 
fphere, and covering its fuperficies to a certain depth ; 
which I think it mud certainly do. I diall not here 
fpeak my opinion how far this fire is the caufe of 
vapours afcending, becaufe I fhall trouble you with 
