Of heat and cold, as of wit and madness, it may be said that “thin
partitions do their bounds divide.” Thus, paint one-half of the surface
of a tin-pot with a mixture of lamp-black and size, and leave the other
half, or side, bright; fill the vessel with boiling water, and by
dipping a thermometer, or even the finger, into it shortly after, it
will be found to cool much more rapidly upon the blackened than upon
the bright side of the pot.