86 grains of water;
at 50 degrees, 4.10 grains; at 60 degrees, 5.77 grains; at 70 degrees,
8.01 grains; and at 90 degrees as much as 14.85 grains. If saturation be
represented by 100, more rapid evaporation from the skin will take place
at 70 degrees, and 75 per cent. of saturation, than at 60 degrees when
saturated, although the absolute quantity of moisture in the air is
greater at the first named temperature than at the latter. As regards the
lungs, however, the case is different, as the air breathed out is, if the
respirations be regular and fairly deep, completely saturated with
moisture at the temperature of the body. In cold climates the amount of
moisture and of the effete matters given off from the lungs in the expired
air is much greater than in hot climates, and the body is also cooled by
the evaporation of water in the form of aqueous vapor. Moist air is a
better conductor of heat than dry air, which accounts for much of the
discomfort felt in winter when a thaw takes place as compared with the
feeling of elasticity when the air is dry. In cold weather, therefore,
moist air cools down the skin and lungs more rapidly than dry air, and
colds consequently result. London fogs are injurious, not only on account
of the various vapors given off by the combustion of coal, but in
consequence of the air being in winter generally saturated with moisture
at a low temperature.
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