DOUGLASS 



PLATE 10 



A. 



B. 



A. The automatic optical periodograph. 



B. Differential patterns of Sequoia record, 3200 years at 11.4. 



B.C 



-1300 



B.C. 

 -1000 



B.C. 

 1-500 



AD 

 500 



A.D. 



-1000 



A.D. 

 -1500 



A.D. 

 -1900 



