28 



CLIMATIC CYCLES AND TREE-GROWTH. 



few isolated peaks. The mountains are covered with pines from their 

 crests to a little below the level of the city. 



This Prescott group was obtained in 1911 for the purpose of testing 

 the conclusions derived from the Flagstaff trees some years earlier. 



Year 1870 



1880 



1890 



1900 



2.0 

 1.0 



0.0 

 2.0 



1.0 



I o.o 



E 

 2.0 



E 



c 



s 



bo 



lo.o 



< 2.0 



1.0 



0.0 

 2.0 



1.0 

 0.0 



/\A 







A 



/\ 



1910 



Group I 

 Trees 1-10 



Group II 

 Trees 11-35 



Group III 

 Trees 36-50 



Group IV 

 Trees 51-60 



Mean of 



all trees 



1-70 



1870 1880 1890 1900 191Q- 



FIG. 6. Annual growth of trees near Prescott, Arizona. 



It consists of 67 trees selected in 5 subgroups depending on their 

 nearness to town. The farthest was 10 miles southeast and the 

 nearest was 1 mile south. It was apparent that the agreement between 

 growth and precipitation increased as the location of the actual rain- 

 fall station was approached. The nearest subgroup, containing 10 



