thing for a full egg is a very heavy thing for air to lift. If you want
to make the experiment, you had better boil the egg quite hard first, and
then you may very safely try to blow it from one cup to the other, with a
little care.
I have now kept you long enough upon this property of the weight of the
air, but there is another thing I should like to mention. You saw the way
in which, in this popgun, I was able to drive the second piece of potato
half or two-thirds of an inch before the first piece started, by virtue of
the elasticity of the air just as I pressed into the copper bottle the
particles of air by means of the pump. Now, this depends upon a wonderful
property in the air, namely, its elasticity; and I should like to give you
a good illustration of this. If I take anything that confines the air
properly, as this membrane, which also is able to contract and expand so
as to give us a measure of the elasticity of the air, and confine in this
bladder a certain portion of air; and then, if we take the atmosphere off
from the outside of it, just as in these cases we put the pressure on if
we take the pressure off, you will see how it will then go on expanding
and expanding, larger and larger, until it will fill the whole of this
bell-jar, shewing you that wonderful property of the air, its elasticity,
its compressibility, and expansibility, to an exceedingly large extent,
and which is very essential for the purposes and services it performs in
the economy of creation.
We will now turn to another very important part of our subject,
remembering that we have examined the candle in its burning, and have
found that it gives rise to various products. We have the products, you
know, of soot, of water, and of something else which you have not yet
examined. We have collected the water, but have allowed the other things
to go into the air. Let us now examine some of these other products.
Here is an experiment which I think will help you in part in this way. We
will put our candle there, and place over it a chimney, thus. I think my
candle will go on burning, because the air-passage is open at the bottom
and the top. In the first place, you see the moisture appearing that you
know about. It is water produced from the candle by the action of the air
upon its hydrogen. But, besides that, something is going out at the top:
it is not moisture it is not water it is not condensable; and yet, after
all, it has very singular properties. You will find that the air coming
out of the top of our chimney is nearly sufficient to blow the light out I
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