esert. Yuma, at the junction of the Gila and Colorado rivers, is
approximately its geographical center. The general aspect of the
country is low and flat and in the Salton sink the dry land dips
several hundred feet below the level of the ocean. Only by extreme
siccity is such land possible when more water rises in evaporation than
falls by precipitation. There are but few such places in the world,
the deepest one being the Dead Sea, which is about thirteen hundred
feet lower than the ocean.

The Colorado Basin is the dry bed of an ancient sea whose shore line is
yet visible in many places upon the sides of the mountains which
surround it. Its floor is composed of clay with deposits of sand and
salt. Strong winds sometimes sweep over it that shift and pile up the
sand in great dunes. The entire region is utterly bare and desolate,
yet by the use of water diverted from the Colorado river it is being
reclaimed to agriculture.

The rainfall is very scant the average annual precipitation at Yuma
being less than three inches. The climate is not dry from any lack of
surface water, as it has the Gila and Colorado rivers, the Gulf of
California and the broad Pacific Ocean to draw from. But the singular
fact remains that the country is extremely dry and that it does not
rain as in other lands.

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 effec