THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. XIIL] July, 1922. [Xo. 11. 



A Rainfall Period Equal to One-ninth the 

 Sun-spot Period. 



DIXSMORE ALTER. 



SYNOPSIS. 



PRELIMINARY discussions based on the rainfall of the United 

 States have been published in the Monthly Weather Review and 

 the Unhersity of Kansas Science Bulletin. The present paper com- 

 pletes the investigation of this period, using much longer records 

 and the data from the United States. Northern Europe. Central Si- 

 beria, the Punjab in India, Chile, South Australia, Jamaica and 

 Madagascar. Numerous tables and curves are given. The con- 

 clusion reached is that the period does exist, and that the relation- 

 ship to sun spots is not a direct one, but due to an unknown common 

 cause. In purely continental areas, minimum rainfall is connected 

 with a maximum of sun spots; in purely marine, with a minimum of 

 sun spots. For areas with rainfall between these types the period 

 is not plainly found. 



INTRODUCTORY. 



In August. 1915, Dr. A. E. Douglass read a very interesting paper 

 before the Berkeley meeting of the American Astronomical Society 

 regarding an investigation of the growth of trees in many parts of 

 the world, indicating an eleven-year period in rainfall (1). 



It seemed to me that the data collected by the Weather Bureau 

 should definitely settle such a question of periods. Some prelimi- 

 nary reading showed, however, that a tremendous amount of time 

 had been spent on the problem (2), and that if solvable it must be 

 very complicated. Other work prevented starting any actual in- 

 vestigation ; then the war intervened and the problem was untouched 

 till the spring of 1919. The first data examined were those from 



(17) 



2 — Science Bui. — 3728 



