The state of the air with respect to the vapor that it contains is
called its humidity. The humidity is said to be high when the air is
damp, and low when the air is dry. Humidity and moisture in the air are
important factors about the weather. It is lack of humidity that has
more to do with poor health, colds, and catarrh than anything else. The
importance of proper humidity in houses and buildings cannot be
emphasized too greatly. Proper humidity will save twelve and one-half
per cent in the cost of heating. The great majority of people are under
the impression that colds are caused by sudden change in temperature,
but the most colds are actually caused by stuffy, hot rooms. The reason
that some people complain that 70° is not hot enough is because the
humidity is too low, but if the moisture is brought into the air at a
proper degree, the humidity is maintained. You will find that 68° will
be a proper temperature to maintain in a room. The reason for this is
that the air in the room is dry and the heat actually goes through it.
In other words, it does not warm it; moist air stops radiation.
Consequently, the result is that it warms it. In other words, moisture
is nothing more than clothing, and this accounts for the fact that in a
hot room, where there is no moisture, we heat our rooms beyond the
degree that is necessary in order to feel any reasonable amount of
comfort. Dry air allows too much radiation from the body and too rapid
evaporation, which makes us cold.
The following experiment illustrates the above statement. Place a few
drops of water on a smooth surface, such as a table top or ordinary
board, and over this a watch glass, containing a small quantity of
ether. In order to hasten evaporation, blow a current of air across it,
and it will be found that the glass will be frozen to the board. This is
caused by the evaporation of the ether, which uses up heat.
You know a great many times when you go out into the wind how cold it
feels, and yet if the wind would actually stop, you would think it warm.
It is the wind that causes the rapid evaporation and makes the surface
of the skin feel cold. As it is true that the moisture in the air acts
as a blanket to us in our homes, it is likewise as true that the vapor
in its natural form outside of the house acts as a blanket for the
earth. Do you realize that without this blanket we would burn up in the
summer and freeze to death in the winter?