The excess of animal heat is carried off, by perspi- ration ; and its diminution is supplied, by internal organization [inorg.

Chem.

171].

The imperfect conducting power of the earth, preserves an equable temperature to the roots of plants.

It is so bad a conductor of heat, that at 100 feet under its surface, the mean temperature in England 52, and in Cairo 70 is always maintained.