THUNDER STORMS, 89 
ing in dew, mift or rain upon the furface of the earth from 
whence they fprang. 
Thefe vapors are either detached in ftreams from the 
humid ground by the influence of the fun, or thrown off 
by the perfpirations of thofe infinite multitudes of animals 
and plants which cover the face of the earth*, or fupplied 
by evaporation, from the ocean, or other grand collections 
of water. 
Ignorant as we are of the nature of thefe operations, and 
of the manner in which they are performed, it is natural 
to fuppofe, that the vapors themfelves afcend in the fame 
electric ftate, whether pofitive, neutral or negative, with 
the fubftances from which they arife. Accordingly fignior 
Seccaria, in making fome of his experiments, obferved, 
that “ fteam rifing from an electrified eolipile diffufes it- 
“¢ felf with the fame uniformity with which thunder clouds 
“ fpread themfelves and {well into arches, extending itfelf 
“ towards any conducting fubftancef.” This ftream then 
was electrified as well as the eolipile from whence it pro- 
ceeded. The fea muft neceffarily be fuppofed, in common 
with the whole terraqueous mafs, to contain juft its natu- 
ral quantity of the electric fluid, and no more: We may 
therefore conclude that both the vapors which arife imme- 
diately from it, and the air which fuftains them, and from 
its fituation enjoys a more equable temperature, than that 
over the land, are in the fame eleétrical ftate with the fea 
itfelf, containing neither more nor /e/s than their natural 
quantity. 
Confidering the vaft extent of the ocean, and the com- 
paratively fmall degree of moifture of which thedry land is 
fufceptible, we may conclude, that a very {mall proportion 
of the clouds which are formed in the atmofphere are ex- 
haled from the latter, and that the ocean is the grand 
fource from whence they principally derive their origin. 
M Our 
* See Hales’s vegetable ftatics, and Chambers’s cyc/oped, under the word, Per‘piration. 
+ Prieftley’s Hiltory, page 327. 
