CLIMATE OF THE SANTA CATALINA MOUNTAINS. 



51 



than are now in hand. During the years 1907 to 1912 the percentage 

 at Benson, Arizona (3,523 feet), was 60 per cent, that at Globe, Arizona 

 (3,525 feet), was 42.1 per cent, the average of the two 51.0 per cent. 

 The average of the percentages for Fort Huachuca (5,100 feet), Fort 

 Apache (5,200 feet), and Bisbee (5,500 feet) is 55.5 per cent. Although 

 these figures indicate that up to 

 5,000 feet there is about the same 

 percentage that holds at 2,400 feet 

 (at Tucson), nevertheless at Flag- 

 staff (6,907 feet) the summer rain 

 was only 40.7 per cent of the total 

 in the years mentioned. At Chlar- 

 son's Mill (7,200 feet) an incom- 

 plete record indicates that in 1907, 

 1909, and 1910 the summer rain 

 was far below the percentages for 

 Tucson for those years. At Greer 

 (9,200 feet), on the Mogollon Pla- 

 teau, the summer rain was a much 

 greater percentage of the annual total in 1905 than it was at Tucson, 

 while in 1906 and 1908 the percentages were nearly identical. It can 

 only be said, therefore, that a much larger body of data is necessary to 

 determine the possible change of seasonal distribution of rain due to 

 altitude. The evidence at hand indicates that there is little probability 

 of a marked influence. (See table 3.) 



TABLE 3. The average annual rainfall for 1907 to 1912, the average summer rainfall for the 

 same years, and the percentage of the latter to the former for stations at different altitudes 

 in central and southern Arizona. 



SEPT OCT NOV OEC. 



Fio. 4. Diagram showing monthly distribution 

 of rainfall at Tucson. Averages of record for 

 38 years, 1876 to 1913 inclusive. 



ALTITUDINAL INCREASE OF RAINFALL. 



The measurements of summer rainfall on the Santa Catalina Moun- 

 tains were begun in 1907 by the installation of a metal gauge at 7,600 

 feet, where the record was secured until 1911, after which it was re- 

 moved to a nearby ridge at 8,000 feet. During 1908 and 1909 readings 

 were secured at the base of the mountain and at 6,000 feet, in 1910 at 



