In regard to the warmth of air, the thermometer is not an exact index
of its temperature. For all bodies are constantly radiating their heat
to cooler adjacent surfaces until all come to the same temperature.
This being so, the thermometer is radiating its heat to walls and
surrounding objects, in addition to what is subtracted by the air that
surrounds it, and thus the air is really several degrees warmer than
the thermometer indicates. A room at 70 degrees by the thermometer is
usually filled with air five or more degrees warmer than this.
Now, the cold air is denser than warm, and therefore contains more
oxygen. Consequently, the cooler the air inspired, the larger the
supply of oxygen and of the vitality and vigor which it imparts. Thus,
the great problem for economy of health is to warm the person as much
as possible by radiated heat, and supply the lungs with cool air. For
when we breathe air at from 16 to 20 degrees, we take double the amount
of oxygen that we do when we inhale it at 80 to 90 degrees, and
consequently can do double the amount of muscle and brain work.
Warming by an open fire is nearest to the natural mode of the Creator,
who heats the earth and its furniture by the great central fire of
heaven, and sends cool breezes for our lungs.
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