PAPERS ON BIOLOGY AND AGRICULTURE 183 



Kishwaukee river in southwestern McHenry County. This is 

 sufficiently close to the Rock River region of Ogle County 

 and sufficiently like it to furnish results for the different 

 seasons (seasonal averages) that are quite comparable. 

 Indeed, it is probable that this McHenry County record 

 furnishes very good information of what the four different 

 seasons of the years involved were throughout the northern 

 part of the whole state. The Marengo records run from 

 1850 to 1917 for precipitation, with but very few breaks in 

 only three years out of these sixty-eight. The temperature 

 records run from 1856 to 1917, with but very few breaks 

 in only two years out of these sixty-two. For the purposes 

 of this paper seasonal figures have been calculated. The 

 U. S. Weather Bureau practice of calling December of 

 the previous year with .January and February of the cur- 

 rent year the winter season of the current year has been 

 followed. Then the spring season consists of March, April 

 and May of the current year, with the summer and autumn 

 seasons June. July, August, and September, October, No- 

 vember of the current year. For temperature the means 

 of the four seasons (average monthly temperatures), and 

 the annual means, are given. For precipitation the means 

 of the four seasons (average monthly precipitation), and 

 the annual totals are given. The former is expressed in 

 degrees Fahrenheit and the latter in inches of rainfall. 

 For making these seasonal calculations the records of 

 monthly mean temperatures and annual temperatures, and 

 the monthly precipitation and annual precipitation figures 

 were used.* These monthly figures are not given in this 

 paper, however, since it is believed that, for furnishing data 

 representative of conditions in Ogle County, the seasonal 

 monthly averages are better. The three pages following 

 give this data for the different years in tabular form. As a 

 sort of norm for the comparison the following average 

 monthly precipitation figures for the different seasons have 

 been calculated from published data,** for the northern 

 central portion of Illinois. 



•Monthly Wea. Rev. Washington, Feb. 1888, p. .=1.'^. 

 111. Climate & Crops Rep. s. 1901-1910. 

 U. S. Wea. Bur. Climatological Data, 1910-1917. 

 U. S. Wea. Bur. Springfield, 111., Records 1888-1900. 



••Kincer, J. B. : Seasonable distribution of precipitation and its frequency 

 and intensity in the U. S. Month. Wea. Rev. 47:624-31, 1919. 



