96 BOTANICAL FEATURES OF NORTH AMERICAN DESERTS. 
is about 7 times as great as the normal precipitation, while at Yuma, 
Arizona, it is more than 35 times as great as the average or normal 
amount of precipitation. The evaporation at the last-named locality 
amounted to 160 times as much as the precipitation in the year 1899. 




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Fic. 4.—Location of and annual precipitation at certain stations in the arid 
region of western America. Chiefly from records of the U.S. Weather Bureau. 
(Reprinted from Publication No. 6.) 
The arid area to the northeastward and leeward of the higher portion 
of the main range of peninsular California, however, can scarcely exceed 
this limit, although no measurements have been made. Near Bay San 
Felipe were seen wheel-tracks which had been made sixteen years before, 
while it is currently reported that the deep ruts of the gun-carriages of the 
