CHAPTER XII.
4.—EVAPORATION.
Q. What is meant by evaporation?
A. The dissipation of liquid by its being converted into vapour.
Q. What effects are produced by evaporation?
A. The liquid vaporized absorbs heat from the body whence it issues; and the body deprived of the liquid by evaporation, loses heat thereby.
Q. If you wet your finger in your mouth, and hold it up in the air, why does it feel cold?
A. The saliva quickly evaporates; and (as it evaporates) absorbs heat from the finger, which makes it feel cold.
Q. If you bathe your temples with ether, why does it allay inflammation and feverish heat?
A. Ether very rapidly evaporates; and (as it evaporates) absorbs heat from the burning head, producing a sensation of cold.