Cycles of Rainfall 27 



discovered for the Ohio Valley are likewise the cycles 

 that exist in the heart of the grain producing area. 



Among the states of the Middle West, Illinois is 

 probably the most highly representative of American 

 cereal production. It produces the largest crop of 

 corn, 1 which is the leading American cereal, and it 

 ranks second in the production of oats. Most of the 

 other cereals that are produced in the upper Mississippi 

 Valley are likewise cultivated with success in Illinois. 

 Another fact that makes Illinois a desirable state for 

 our purpose is that its meteorological records are fairly 

 long and are obtainable from so many stations as to be 

 representative of the weather conditions in the entire 

 state. This last fact is all-important if the statistics 

 for crop production of the whole state are to be con- 

 sidered in relation to the weather cycles of the state. 



In Table III of the Appendix to this chapter the 

 record of the annual rainfall in Illinois is given for a 

 period of 41 years. 2 The ideal direct method with 



1 This statement was accurate when it was first written. But in 

 1912 Iowa gained by a narrow margin the first place among the corn 

 producing states. 



2 The raw data were taken from Bulletin W of the Weather Bu- 

 reau of the United States and from the Annual Reports of the Chief 

 of the Weather Bureau. The stations used in computing the mean 

 annual rainfall were: — In Northern Illinois: Aurora, Cambridge, 

 Chicago, Tiskilwa, Galva, Kishwaukee, Ottawa, Winnebago, and 

 Henry. In Central Illinois: Charleston, Carlinville, Coatsburg, 

 Decatur, Griggsville, Knoxville, Havana, LaHarpe, Pana, Peoria, 

 and Springfield. In Southern Illinois: Cairo, Cobden, Carlyle, 

 Golconda, Flora, Greenville, McLeansboro, Mascoutah, Mt. 

 Cannel, and Palestine. 



All of these stations do not present full records for the 41 years, 



