Let us now take the case of water changing into ice: we can effect that by
cooling it in a mixture of salt and pounded ice[12]; and I shall do so to
shew you the expansion of water into a thing of larger bulk when it is so
changed. These bottles [holding one] are made of strong cast iron, very
strong and very thick--I suppose they are the third of an inch in
thickness; they are very carefully filled with water, so as to exclude all
air, and then they are screwed down tight. We shall see that when we
freeze the water in these iron vessels, they will not be able to hold the
ice, and the expansion within them will break them in pieces as these
[pointing to some fragments] are broken, which have been bottles of
exactly the same kind. I am about to put these two bottles into that
mixture of ice and salt, for the purpose of shewing that when water
becomes ice, it changes in volume in this extraordinary way.
In the mean time look at the change which has taken place in the water to
which we have applied heat--it is losing its fluid state. You may tell
this by two or three circumstances. I have covered the mouth of this glass
flask, in which water is boiling, with a watch-glass. Do you see what
happens? It rattles away like a valve chattering, because the steam rising
from the boiling water sends the valve up and down, and forces itself out,
and so makes it clatter.
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