08 



THE IRRIGATION AGE. 



only endurable, but even enjoyable and re- 

 freshing. These are the facts as they ex- 

 ist now, when the present conditions the 

 bare soil, etc. are specially conductive to 

 high temperatures. But it may be readi- 

 ly conceived that there will take place sa- 

 lubrious modifications, as some of us have 

 already realized, when these desert places 

 are covered with the green carpet of al- 

 falfa and the verdure of trees; -when the 

 wasting waters are stored and diverted by 

 the irrigator to the surface of a soil only 

 waiting for water to produce bountifully, 

 not only the fruits of the earth in due sea- 

 son, but almost to produce the seasons 

 themselves at will." 



In the nature of the case we could not 

 expect any definite scientific data for this 

 vicinity prior to the practice of irrigation. 

 The precipitation is about seven inches 

 per annum. Settlement and residence 

 are impracticable in a locality in which 

 agriculture must depend for moisture sole- 

 ly upon irrigation. In the Salt River 

 Valley, settlement and irrigation came 

 hand in hand. 



The Salt River Valley, with Phoenix as 

 its center, is situated in the vicinity of the 

 33d parallel of north latitude. 



The surrounding physical and climatic 

 conditions are totally different from those 

 of any other locality under irrigation, and 

 must be understood in order to arrive at 

 right conclusions. 



It has an elevation ranging from 1,000 

 to 1,500 feet above sea level. 



High mountain ranges surround it on 

 all sides, save on the southwest, where it 

 verges into the larger Gila Valley. 



The Gila Valley, under similar condi- 

 tions, extends to the Gulf of California, 

 which in turn extends with its 53,000 

 square miles of surface well into the trop- 

 ical zone. 



This great, inland sea, with its mouth 

 250 miles wide, flanked on either side with 

 continuous mountain chains, acts as a 

 funnel into which the tropical waters and 

 winds sweeping from the equator up the 

 Mexican coast, enter. 



These surroundings and winds are large- 

 ly the influences which go to produce our 

 peculiar and phenomenal climatic condi- 

 tions. 



It is universally conceded that an at- 

 mosphere carrying too much moisture is 

 unfavorable to perfect health. It may 

 not be so well known, but is equally cer- 



tain that the air may be too dry. A couple 

 of my patients had this experience. Dur- 

 ing a long drive upon the desert, on an 

 exceedingly hot day, the air became ex- 

 tremely dry and fairly burned. Their 

 throats became parched and perspiration 

 ceased. No amount of water taken inter- 

 nally seemed to relieve this condition, 

 which was speedily followed by a languor 

 and then stupor, bordering on coma. This 

 thoroughly alarmed the wiser of them, 

 and sensibly, during the remainder of the 

 day they took turns, fifteen minutes in 

 duration, one driving while the other grat- 

 ified the irresistible desire to sleep, and 

 in this way they reached irrigated ground 

 in safety. The same phenomena have been 

 observed in numerous other cases. I am 

 satisfied this explains many cases of death 

 upon the desert which have heretofore 

 been attributed to lack of water. During 

 the summer time, in this locality, elimina- 

 tion by the kidneys is reduced one-half. 

 Perspiration is immensely increased and 

 the skin becomes the chief eliminating or- 

 gan of the system. When the percentage 

 of humidity in the air gets below a cer- 

 tain point, evaporation from the surface of 

 the body becomes too instant, the surface 

 burns, perspiration and elimination of ef- 

 fete material ceases, thus producing the 

 phenomena above described. I attribute 

 these effects entirely to alack of sufficient 

 moisture in the atmosphere. 



I am not prepared, as yet at least, to fix 

 definitely the point at which the percent- 

 age of moisture in the air is neither too 

 great or too little. Investigation may, 

 and probably will, show that the most 

 favorable degree of saturation would vary 

 according to individual characteristics. It 

 is probable there is a range of 10 or 12 

 degrees within which it is difficult, if not 

 impossible, to say that any given point 

 would be more favorable to general health 

 than another. It may be safely said that 

 in the temperature of the Salt River 

 Valley, during the summer, a humidity 

 below 8 per cent is disadvantageous, while 

 that above 20- per cent begins to become 

 oppressive. 



Both actual and sensible temperature, 

 as shown respectively by the readings of 

 dry and wet bulb thermometers, must 

 always be considered in connection with 

 the humidity. In every climate there are 

 seasons when the percentage of humidity 

 is excessive, and results generally in a 



