[ 134 ] 
ftate, when they have pafTed the furrounding fluid, 
they muft be repelled by it ; and alfo repel each' 
other ; and if each particle of vapour, and its fur- 
rounding fluid, occupy a greater fpace than the fame 
weight of air, they mufl: be fitted to afeend till they 
come in aequilibrium with the upper and rarer part of 
the atmofphere ; where they mufl; float, until their 
fpecific gravity is altered. As it is very difficult to 
aflign the magnitude of each particle of vapour and 
exhalation, and that of the furrounding fluid ; and 
to fliew, that both, taken together, occupy a greater 
portion of fpace than the fame weight of air ; we 
can only apply to experiment, to fhew, that it is pof- 
fible that it may be fo j and that will fhew, that in all 
probability it is fo ; fince it is evident, that every 
particle mufl be endued with a portion of this elec- 
trical fire or fluid, and that there is not any other 
fufficient caufe affigned for their afeending. 
It is evident, that, upon eledrifying any light 
matter, fuch as down, or the downy parts of feathers, 
their fpecific gravity is much leflened ; and that, 
by holding another eledrified body under them, they 
may be driven upwards at pleafure. It is alfo evi- 
dent, from experiment, that the more you divide the 
parts of fuch bodies, the more of their fpecific gra- 
vity they will loofe by being eledrified j and by di- 
viding them into very minute parts, I have found, 
that they afeended to a confiderable height after they 
were eledrified. From whence I think it highly 
probable, that the exceeding fmall particles of va- 
pour and exhalation may be, and are, fufficiently 
eledrified to render them fpecifically lighter than the 
lower air j and that they do afeend by that means. 
And 
