131 



THE THIRD PROPOSITION, 



That the least rain should be in the deserts, is confirmed by the records 

 kept at various stations; commencing south and proceeding north: 



The Colorado and Mohave Deserts are in the zone where the great 

 body of the descending southwest return trade winds reach the earth. 

 It has been shown that these descending currents cannot give rain, 

 as, in falling, they continuously arrive at regions of increasing tem- 

 perature. It is, therefore, in this zone, on both sides of the equator, 

 that almost all the great deserts of the earth are situated, and pri- 

 marily to this cause is their existence due. The Mohave and Colo- 

 rado Deserts are in the same latitudes north of the equator as the 

 Deserts of Sahara and Arabia. The great desert of the interior of 

 Australia is in the same latitude south of the equator as the Desert 

 of Atacama, in South America. 



The stations of Wadsworth, Hot Springs, and Brown's, in the 

 above table, are in Nevada, and in the region of variable winds, and 

 are made desert by want of rain ; but better illustrate the last propo- 

 sition that less rain should fall on the opposite side of the mountains 

 to that exposed to the moisture bearing winds. For further illustra- 

 tion of the proposition, I have selected stations in different parts of 

 this State and Nevada. Fort Tejon, latitude thirty-four degrees fifty- 

 three minutes north, longitude one hundred and eighteen degrees 

 fifty-three minutes west, on the south side of the Tehachapi Moun- 

 tains, where the Sierra Nevada and Coast Range unite, forming a 

 wall against the southeast wind, has an elevation of three thousand 

 two hundred and forty feet. From a record of five years, it has an 

 annual mean of nineteen and fifty-three one-hundredths inches of 

 rain. Caliente, a station of the Southern Pacific Railroad, thirty 

 miles northeast, elevation one thousand two hundred and ninety feet 

 upon the north side of this range, from a record of two years, has 

 but an annual mean of six and thirty-eight one-hundredths inches; 

 and Sumner, thirty-one miles north of Tejon, with an elevation of 

 four hundred and fifteen feet, receives but three and ninety-two one- 

 hundredths inches. The Tehachapi Mountains precipitate some of 

 the moisture from the southeast winds, and, under the law as stated 

 by Guyot, they descend into the valley dry and cloudless. 



The summit of Mount Diablo, elevation three thousand eight hun- 

 dred and fifty-six feet, from a record of two years, receives an annual 

 mean of twenty and eighty-five one-hundredths inches. Livermore, 



