178 
GARDENING AS A SCIENCE. 
To understand the philosophy of the deterioration of air by burning candles, 
we must observe that it is composed of two aerial fluids now called gases ; 
one, and the chief as respects bulk, is the gas named azote, a word derived from 
the Greek a, (from, or contrary to,) an&zoe, (life,) — this compound word expresses, 
then, the destructive quality . of the gas, it being fatal to the organs of respiration. 
Now, as four parts of five of the atmosphere consist of this deadly air, it should 
appear surprising that the air we breathe is not, of itself, a medium of poison. 
But, mixed with the azote is another air or gas so energetic, so essentially vital, 
that although the volume it occupies is not greater than one-fifth of the whole, 
it entirely qualifies and subdues the noxious properties of the azote. This gas 
is termed oxygen. If four pints by measure of the former, be blended with 
one pint of the latter, an air will be produced exceedingly similar to, if not 
identical witli atmospheric air, so far as respects its powers to sustain breathing 
life, and combustion. Whatever be the nature of the union which exists between 
these two chief elements of air, certain it is that burning bodies attract the 
vital principle from it, and leave the azote deprived of power to sustain either 
life or flame. In proof of this assertion, and thus in a degree to apply the discovery 
of Dr. Priestley, let a deep bell-glass, or glass shade, capable to contain a gallon, 
or more, be inverted over a dish, or other vessel, wherein its rim may dip an inch 
deep in water. Place a wax candle in a socket, weighted at bottom, so as to 
stand firm and erect in the dish, the entire candle being several inches above the 
surface of the water. The candle being lighted, invert the glass (which it is plain 
will contain air, and nothing else) over it. At first, a small portion of water will 
be expelled under the rim, in consequence of the expansion of the rarified air ; but 
gradually, it will enter again into the glass, and rise above its former level. By 
degrees the flame of the candle will become more feeble, and finally be extin- 
guished, when, if the first water-level have been accurately marked, and the 
contents of the bell ascertained, it will be seen that the water will have risen 
somewhere about one-fifth higher than it stood originally. 
This experiment will suffice to prove that the air remaining in the glass can 
no longer sustain combustion ; and if a mouse, or other small breathing animal be 
passed adroitly under the water into the depraved air (and this is readily effected 
by means of a chemical water-trough) it will immediately appear much distressed, 
and soon perish by suffocation. But the experiment is not chemically accurate, 
for, although the vital oxygen has been nearly attracted from the air, yet, as the 
cotton, and wax, or tallow of the candle, contain other elements of vegetable 
matters, which will form the subject of future notice, those elements yield a gas 
and watery vapour, that blend in part with the azote of the air remaining in the 
glass, and render it in a degree compound. 
Our readers will now perceive that atmospheric air consists chiefly of the gas 
azote, and the gas oxygen, the former constituting about f ths of the entire volume ; 
and that in every act of ordinary combustion, the fifth part — that is the oxygen, 
is attracted by the burning body, leaving the azote in its natural condition, fatal to 
