264 



AGRICULTURAL INDICATORS. 



* Unpublished data from the OflSce of Cereal Investigations, Bureau of Plant Industry, U. S. 

 Department of Agriculture. 



Ball and Rothgeb (1918: 22) have given a very instructive account of the 

 distribution and timeliness of the rainfall of the various years in relation to 

 yield. Their discussion makes clear the number of apparently chance factors 

 which enter into the production of a crop. In spite of this, however, both the 

 11-year and the 2 to 3 year cycle can be recognized in the production as well 

 as in the rainfall. As seems to be the rule, these show more clearly in the 



IflOQ 



1905 



1910 



1915 



Fio. 16. Graph of total and seasonal rainfall at Williaton, North Dakota. 



