Neither is the rainfall deficient from any lack of evaporation.
Upon the contrary the evaporation is excessive and according to
the estimate of Major Powell amounts fully to one hundred inches
of water per annum. If the vapors arising from this enormous
evaporation should all be condensed into clouds and converted
into rain it would create a rainy season that would last
throughout the year.
The humidity caused by an abundant rainfall in any low, hot
country is usually enough to unfit it for human habitation. The
combined effect of heat and moisture upon a fertile soil causes
an excess of both growing and decaying vegetation that fills the
atmosphere with noxious vapors and disease producing germs. The
sultry air is so oppressive that it is more than physical
endurance can bear. The particles of vapor which float in the
atmosphere absorb and hold the heat until it becomes like a
steaming hot blanket that is death to unacclimated life. All of
this is changed where siccity prevails. The rapid evaporation
quickly dispels the vapors and the dry heat desiccates the
disease creating germs and makes them innocuous.
The effect of heat upon the body is measured by the difference in
the actual and sensible temperatures, as recorded by the dry and
wet bulb thermometers. When both stand nearly together as they
are apt to do in a humid atmosphere, the heat becomes
insufferable. In the dry climate of Arizona such a condition
cannot occur. The difference in the two instruments is always
great, often as much as forty degrees. For this reason, a
temperature of 118 degrees F. at Yuma is less oppressive than 98
degrees F. is in New York. A low relative humidity gives comfort
and freedom from sunstroke even when the thermometer registers
the shade temperature in three figures.
A dry, warm climate is a stimulant to the cutaneous function.
The skin is an important excreting organ that is furnished with a
large number of sweat glands which are for the dual purpose of
furnishing moisture for cooling the body by evaporation and the
elimination of worn out and waste material from the organism. As
an organ it is not easily injured by over work, but readily lends
its function in an emergency in any effort to relieve other tired
or diseased organs of the body. By vicarious action the skin is
capable of performing much extra labor without injury to itself
and can be harnessed temporarily for the relief of some vital
part which has become crippled until its function can be
restored.
A diseased kidney depends particularly upon the skin for succor
more than any other organ. When the kidneys from any cause fail
to act the skin comes to their rescue and throws off impurities
which nature intended should go by the renal route.
