practical papers—the atmosphere . 367 
mal organisms, and mineral substances of our planet were once 
suspended in the atmosphere. To the formation and growth of 
these gigantic vegetable forms, the immense zone of carbonic 
acid contributes its wealth of carbon,—to be retained, locked 
safely in the strong receptacles of the earth till the necessities of 
the race lead to the discovery of the treasure,—whilst the oxygen, 
hoiden in combination, has been rendered back, in purity, to min¬ 
gle with the nitrogen, and thus form an atmosphere capable of 
sustaining the higher forms of animal life. When we consider 
that this aerial ocean, in the lower strata of which we live, is ab¬ 
solutely essential to all the higher forms of animal life, and that, 
with the exception of a few salts, the totality of plant food is, by 
the chemistry of the leaf, elaborated from the air; that this gase¬ 
ous envelope, the sole conveyer of speech and means of commu¬ 
nicating thoughts, forms one vast aerial harp, whose strings in¬ 
constant vibration, bear to the ear of the Creator the discords and 
harmonies of a world of sentient beings; that, deprived of its at¬ 
mosphere, this orb would roll through space a soundless desert, 
we shall realize that it is quite as worthy the study of the intelli¬ 
gent beings dwelling in its depths, as the smaller ocean of water 
which it encloses. 
The gases forming the atmosphere are not in chemical union f 
as are the gaseous constituents of water, but mixed mechanically, 
about four parts of nitrogen to one of oxygen and 1 1000 part of 
carbonic acid. During a thunder storm the electric discharge, 
causing a chemical union of certain volumes of nitrogen with oxy¬ 
gen, result in the formation of nitric acid. Disseminated through 
the aerial ocean are found also those ammoniacal vapors—carbon¬ 
ate of ammonia—from which plants derive their nitrogenus con¬ 
tents. Were these gases subject, like fluids and solids to the sole 
control of gravity, there would exist nearest the earth a zone of 
carbonic acid gas, destroying all animal life, and above this belt of 
oxygen, enveloping all, a vast cloud of nitrogen. But somehow, 
the Creator, for the safety of his creatures has taught these gases 
to laugh at the claims of gravity, and to wander about at their 
own sweet will, mixing one with the other so uniformly that the 
proportion of each gas is found the same in two volumes of air 7 
