238 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



I 3 5 7 9 II 13 15 J7 19 21 23 I 3 5 7 9 II 13 15 17 19 21 23 



FiQUKK 1.— Cur%'es showing the 23-year cycle in thickness of Pleistocene and Eocene varves. (C. Q. Abbot, 

 Solar radiation and weather studies, Smithsonian Misc. Coll., vol. 94, No. 10, fig. 32. 1935.) 



