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198 FRAGMENTS OF SCIENCE.

13. Liquids and their Vapors in relation to Radiant
IIeat.

The deportment here assigned to atmospheric vapor has
been established by direct experiments on air taken from
the streets and parks of London, from the downs of Epsom,
from the hills and sea-beach of the Isle of Wight, and also
by experiments on air in the first instance dried, and after-
ward rendered artificially humid by pure distilled water.
It has also been established in the following way: Ten
volatile liquids were taken at random and the power of
these liquids, at a common thickness, to intercept the waves
of heat was carefully determined. The vapors of the'liquids
were next taken, in quantities proportional to the quantities
of liquid, and the power of the vapors to intercept the waves
of heat was also determined. Commencing with the sub-
stance which exerted the least absorptive power, and pro-
ceeding upward to the most energetic, the following order
of absorption was observed:

Liquids. Vapors.
Bisulphide of carbon. Bisulphide of carbon.
Chloroform. Chloroform.
Iodide of methyl. Iodide of methyl.
Iodide of ethyl. Iodide of ethyl.
Benzol. Benzol.
Amylene. Amylene.
Sulphuric ether. Sulphuric ether.
Acetic ether. Acetic ether.
Formic ether. Formic ether.
Alcohol. Alcohol.

Water.

We here find the order of absorption in both cases to
be the same. We have liberated the melecules from the
bonds which trammel them more or less in a liquid condi-
tion; but this change in their state of aggregation does not

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