THE ELEMENTS. 
209 
Another general quality of the atmosphere is the power 
if evaporating fluids. The adjustment of this quality to 
)jr use is seen in its action upon the sea. In the sea, 
water and salt are mixed together most intimately; yet 
the atmosphere raises the water, and leaves the salt. Pure 
and fresh as drops of rain descend, they are collected from 
brine. If evaporation be solution, (which seems to be 
probable,) then the air dissolves the water, and not the salt. 
Upon whatever it be founded, the distinction is critical; so 
much so, that when we attempt to imitate the process by 
art, we must regulate our distillation with great care and 
nicety, or, together with the water, we get the bitterness, 
or, at least, the distastefulness, of the marine substance: 
and, after all, it is owing to this original elective power in 
the air, that we can effect the separation which we wish, 
by any art or means whatever. 
By evaporation, water is carried up into the air; by the 
converse of evaporation, it falls down upon the earth. And 
how does it fall? Not by the clouds being all at once re¬ 
converted into water, and descending like a sheet; not in 
rushing down in columns from a spout; but in moderate 
drops, as from a colander. Our watering-pots are made to 
imitate showers of rain. Yet, a 'priori , I should have 
thought either of the two former methods more likely to 
have taken place than the last. 
By respiration, flame, putrefaction, air is rendered unfit 
for the support of animal life. By the constant operation 
of these corrupting principles, the whole atmosphere, if 
there were no restoring causes, would come at length to be 
deprived of its necessary degree of purity. Some of these 
causes seem to have been discovered, and their efficacy 
ascertained by experiment. And so far as the discovery 
has proceeded, it opens to us a beautiful and a wonderful 
economy. Vegetation proves to be one of them. A sprig 
of mint corked up with a small portion of foul air placed 
in the light, renders it again capable of supporting life or 
flame. Here, therefore, is a constant circulation of bene¬ 
fits maintained between the two great provinces of organ¬ 
ized nature. The plant purifies what the animal has 
poisoned; in return, the contaminated air is more than 
ordinarily nutritious to the plant. Agitation with water 
turns out to be another of these restoratives. The foulest 
air, shaken in a bottle with water for a sufficient length of 
time, recovers a great degree of its purity. Here then 
again, allowing for the scale upon which nature works, we 
gee the salutary effects of storms and tempests. The yesty 
