160 



THE CLIMATIC FACTOR AS ILLUSTRATED IN ARID AMERICA. 



The first is shown in figure 42, where the precipitation at Porterville is compared directl}' 

 with the growth of young sequoias at Dillonwood between 30 and 40 miles to the east of 

 Porterville and 6,000 feet above it. The measurements used in preparing the two curves 

 of growth here shown consist of group A (46 measurements of 19 trees, none of which 

 was over 100 years of age and most of which were less than 40 years of age) and group 

 B (8 measurements upon 5 trees having an age of from 100 to 150 years). Several of the 



Inches of July Aug. Sep Oct. Nov. Dec. Jan. Feb. Mar. Api. May Jun e 

 rainat ■ ' ' ' ' ''"^ ' ^ I I ' ^incneboi 



Fresno and 



Porterville 



4 



rain at 

 San Fran- 

 8 Cisco 



Fio. 41.— Monthly Distribution of Precipitation in California. 



San Francisco ■ 

 Freano ' 



Porterville 



