THUNDER STORMS. 95 
in feparate parties before they join the main body; and as 
the electrical flates of thefe clouds may be very different 
from each other, from the different electrical ftates of 
thofe parts of the atmofphere in which they gather; the 
general equilibrium of the atmofphere over a country can- 
not be reftored by a fingle difcharge, but fucceflive flafhes 
will dart from cloud to cloud, and betwixt thefe and the 
earth, till at length the whole collected mafs of vapor is 
{pent and diflolved in rain. 
Here a common obfervation naturally occurs, viz. that 
frequently after a flafh of lightening a fudden fhower de- 
{cends in large drops. The mutual attraGlion between the 
vapors and the air, when in this electrical ftate, is fuffici- 
ent to fuftain the former, notwithftanding that they are by 
this attraction greatly condenfed, being as it were forced 
into a phyfical conta@t, both with the particles of air, and 
with each other*. But as foon as the air is reftored to its 
natural electric ftate by a flafh of lightening, this attraction 
ceafes, and the vapors precipitate by their own {pecific 
gravity in a heavy fhower. 
Long and extenfive calms, in certain latitudes and fea- 
fons, take place upon the ocean, during the continuance 
of which, the heat is fcarcely tolerable. (See note, page gt.) 
Where thefe take place the air will naturally undergo the 
fame changes, in its denfity and electric capacity, as the 
air over the land does in the fummer feafon, and, when 
fufficiently 
* A gentleman of my acquaintance, who is both intelligent and curious, informed me fome 
years fince, that he was once upon the top of amountain in Spain, upon which a thunder clouch 
gathered; that as foon as the cloud became infulated from the mountain it difcharged a vio- 
lent tempeft of thunder and lightening upon the plains below; that he never was fo thorough- 
ly foaked in the moft violent {hower as when in the body of this cloud, though without a drop» 
of rain, feeling as if he had been immerfed in a river. This idea is further juitified by the fo- 
lid appearance of the clouds that rife in the weft an a hot fummer’s day, compared with thofe: 
which float in the atmofphere at other feafons ; which fhewsa manifeft difference in their den- 
fity and contexture : And when we obferve attentively the feveral parts of a thunder cloud, the 
diftinétnefs of their borders and their {welling furbeloes; how ftrongly they reflect the rays of 
the fun, thereby exhibiting the moft vivid lights and deep contrafting fhades; and onthe other 
hand obferve the beautiful effe@ts of their refractive power in the intenfe golden {kirts which: 
adorn the rifing cloud with a fetting fun behind it; we muft neceffarily conclude, that, al- 
though the vapors of which fuch clouds confift are colle&ted and condenfed in higher regions of 
the atmofphere than are thofe which ufually form clouds at other feafons, yet their denfity and 
Specific gravity is much greater; and they derive their fupport from the electric principle, 
