31 
covery of modern times,) we perceive these to be very 
strongly marked. There is every reason to believe, that 
had the oxygen and nitrogen been mixed together in any 
other proportions than they are, the atmosphere would not 
have been proper for the support of animal life, and com- 
pounds, of the most deadly nature, are, we know, formed, 
by chemically combining these airs together, in different 
quantities; as for example, the air called nitrous acid gas, 
which consists of four proportionals of oxygen, and one of 
nitrogen, so far from being of a salutary nature, is instantly 
fatal to any animal that inhales it, and the nitric acid, or 
aqua-fortis of commerce, is formed by chemically combining 
other proportions of oxygen and nitrogen. These, how- 
ever are chemical compounds, but the gases of the atmos- 
phere are simply mixed together, and not in chemical union. 
Another important result of the oxygen of the atmosphere 
being diluted with nitrogen is, that the activity of combus- 
tion is kept down by it. Any burning substance put into 
nitrogen is instantly extinguished; but the same ignited 
substance plunged into oxygen, burns with a fury and bril- 
liancy, of which those who have not seen the experiment 
could have no conception. Were the atmosphere composed 
of oxygen alone, the spark from a flint would risk setting 
fire to the globe itself. 
The air contains, also, a little water, and.a very 
small quantity of carbonic acid, but the mixture of 
oxygen and azote we are to consider as the atmosphere ;— 
and of what moment, what importance is it in the great 
economy of nature! We set the highest value on gold, on 
silver, on pearls, on precious stones, but what are these but 
the merest baubles, compared with that beneficent aerial 
fountain of life, which is breathed by every organized being; 
by every man, quadruped, bird, reptile, fish, insect, animal- 
