132 Climatology 



No. 289. DOUGLASS, A. E. Climatic Cycles and Tree-growth. A Study of the 

 Annual Rings of Trees in Relation to Clitnatic and Solar Activity. 

 Octavo, 127 pages, 11 plates, 40 figures. In press. 



This volume describes a study of the correlation between the annual rings 

 of trees and rainfall and solar activity. The rings of the yellow pine, Pinus pon- 

 derosa, in the dry climate of northern Arizona, are found to vary approximately 

 with local rainfall. Ring records by this tree are carried back over 500 years. 

 The growth of the Scotch pine, Pinus silvestris, near the Baltic Sea, varies in 

 cycles closely corresponding to the sunspot cycle. The great sequoia, Sequoia 

 gigantea, whose ring record is carried back over 3,200 years, shows persistent 

 11-year and other short-period cycles. The periodograph, an instrument specially 

 designed for detecting and studying short cycles, is described. 



