Warmth of different Materials.--"The indefatigable Rumford made an
elaborate series of experiments on the conductivity of the substances
used in clothing. His method was this:--A mercurial thermometer was
suspended in the axis of a cylindrical glass tube ending with a globe, in
such a manner that the centre of the bulb of the thermometer occupied the
centre of the globe; the space between the internal surface of the globe
and the bulb was filled with the substance whose conductive power was to
be determined; the instrument was then heated in boiling water, and
afterwards, being plunged into a freezing mixture of pounded ice and
salt, the times of cooling down 136 degrees Fahr. were noted. They are
recorded in the following table:--
Surrounded with -- Seconds.
Twisted silk.................................. 917
Fine lint..................................... 1032
Cotton wool.................................. 1046
Sheep's wool.................................. 1118
Taffety....................................... 1169
Raw silk...................................... 1264
Beaver's fur.................................. 1296
Eider down.................................... 1305
Hare's fur.................................... 1312
Wood ashes.................................... 927
Charcoal.............................
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