burn up more powerfully than the coals for the iron of the grate itself
is even more combustible than the coals which we burn in it. A fire put
into the middle of a locomotive would be a fire in a magazine of fuel, if
the atmosphere were oxygen. The nitrogen lowers it down and makes it
moderate and useful for us, and then, with all that, it takes away with it
the fumes that you have seen produced from the candle, disperses them
throughout the whole of the atmosphere, and carries them away to places
where they are wanted to perform a great and glorious purpose of good to
man, for the sustenance of vegetation; and thus does a most wonderful
work, although you say, on examining it, Why, it is a perfectly
indifferent thing. This nitrogen in its ordinary state is an inactive
element; no action short of the most intense electric force, and then in
the most infinitely small degree, can cause the nitrogen to combine
directly with the other element of the atmosphere, or with other things
round about it; it is a perfectly indifferent, and therefore to say, a
safe substance.
But before I take you to that result, I must tell you about the atmosphere
itself. I have written on this diagram the composition of one hundred
parts of atmospheric air:
Bulk. Weight.
Oxygen, . . . . . 20 22.3
Nitrogen, . . . . 80 77.7
100 100.0
It is a true analysis of the atmosphere, so far as regards the quantity of
oxygen and the quantity of nitrogen present. By our analysis, we find that
5 pints of the atmosphere contain only 1 pint of oxygen, and 4 pints, or 4
parts, of nitrogen by bulk. That is our analysis of the atmosphere. It
requires all that quantity of nitrogen to reduce the oxygen down, so as to
be able to supply the candle properly with fuel, so as to supply us with
an atmosphere which our lungs can healthily and safely breathe; for it is
just as important to make the oxygen right for us to breathe, as it is to
make the atmosphere right for the burning of the fire and the candle.
But now for this atmosphere. First of all, let me tell you the weight of
these gases. A pint of nitrogen weighs 104 10 grains, or a cubic foot
weighs 11 6 ounce. That is the weight of the nitrogen. The oxygen is
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