202 
GARDENING AS A SCIENCE. 
it to undergo its several transformations, it must part with some substance or 
essence, which it had retained in its original gaseous or aerial form. 
Presuming then for the sake of argument, and witli a view to elucidate our 
position, that the atmosphere is the repository of azote, of which it constitutes fths 
of the entire volume, it follows that the state in which it thus naturally exists is 
that of a gas or aerial fluid. But this assumption implies that its particles are 
infinitely divided, and kept asunder by some powerful, repulsive agent; and 
therefore, strictly speaking, azote is a base, capable of being rarified, and vaporized 
by some agency, as mercury is by heat. 
The ethereal essence, or elementary fire that we term electricity, appears to be 
the sole agent wliich can so act upon matter as to reduce it to the condition of a 
permanent gas, and confer on it the power to attract, and unite with other 
substances, thereby producing definite new compounds. If this view be correct, 
azote, and all otlier gaseous fluids, are highly electrized matters, and all chemical 
unions which they form and changes which they undergo, are entirely dependent 
upon electric, mutual attractions ; and thus we may infer the compound nature of 
all gaseous bodies. 
But theory apart, the importance of azote in the aerial volume is paramount ; 
for though deadly in itself, yet, when united to its definite and fixed quantity of 
oxygen, it becomes the principle of life to the animal creation. Again, as the base 
of nitric acid (whence we derive the nitrates of potassa and soda, so valuable to 
husbandry) and of ammonia, it is of vast importance to vegetation. All fermenting 
matters, all animal, and some vegetable substances in a state of putrefaction, pour 
into the atmosphere a stream of ammoniacal gas, which being for a time difl*ased 
throughout it, is conveyed to the earth by mists and rain, and thus fertilizes the 
ground. 
The question of the primary formation of ammonia is dark, but the phenomenon 
must be electrical, for the quantities of the two gases, azote and hydrogen, required 
to form ammonia, occupy twice the volume of a similar quantity, by weight, of 
ammoniacal gas. 
Hydrogen gas is always present in the atmosphere, owing to the decomposition 
of water. When therefore a chemical union of azote and hydrogen is therein 
effected by atmospheric electricity, the gases become condensed into half their 
original volume, proving that the electricities of each have combined and neutra- 
lized each other to a given extent. 
In our laboratories we can effect the converse of this natural experiment, by 
the decomposition of ammoniacal gas, thereby doubling its volume by the separa- 
tion of the elements ; but we fail to produce ammonia by the union of those 
elements. Nature, however, is sufficient to the work — hence, the peculiar softness 
of rain water, and the extremely fertilizing qualities which it possesses. 
Oxygen. — Of this substance we are virtually ignorant, though its name is 
familiar to every one. It was certainly discovered by Dr. Priestley, on the 
