138 CLIMATIC CYCLES AND TREE-GROWTH 



17. Provisional results indicate that the 11-year cycle appears in 

 the long sequoia records at 1300 to 1100 b. c, 300 b. c, a. d. 35 to 

 240; 375 to 475; 600 to 650; 800 to 900 and 1250 onward, with the 

 interruption following 1700. 



18. The dry years in the Flagstaff area tree-growth analyze best 

 on 14- and 21-year cycles with major droughts at about 150-year 

 intervals and minor droughts at 40- or 50-year intervals. 



19. The extension of the cycles observed in the last 200 years in 

 the Flagstaff area indicates possible large growth of trees in the 1930 's 

 and 1950*8, with depressions in the early and late 1940 's. 



It is recognized that much of this work is new and that time is 

 needed to test and improve it, but it is hoped that these preliminary 

 results are not greatly in error. 



