188 ILLINOIS STATE ACADEMY OF SCIENCE 



assumed general average of 35 inches for the year, which 

 would be a high general average, be taken, the figure of 

 37.8 inches is obtained. If this excess of over 35 inches for 

 the phenomenal year 1876 be deducted from the total for the 

 period before 1885 this whole period becomes of the same 

 magnitude as that of the period after 1885. Further, the 

 year 1901, of the latter period, was phenomenally dry, hav- 

 ing a total annual precipitation of only 19.7 inches. Conse- 

 quently it does not appear, on the whole, safe to say that 

 there has really been any change in the rainfall of this re- 

 gion of northern Illinois in more than a half century. 



An inspection of the seasonal monthly means of preci- 

 pitation shows considerable deviation from the normal in a 

 number of single years for each of the four seasons, but 

 there does not appear any change running over a series of 

 years for any of the seasons, within the total period for 

 which data exist. The winters of 1858, 1866, 1872 and 1899 

 show low precipitation, while those for 1876 (which was a 

 year of very phenomenally high precipitation throughout all 

 the four seasons), and 1887 show high precipitation. With 

 the exception of the phenomenally low precipitation of the 

 year 1901 the growing seasons (spring and summer) of the 

 different years show rather a number of individual years 

 with amounts above the usual than years with amounts be- 

 low. The period 1850-1853 appears to have had unusually 

 high precipitation for the growing seasons. The remain- 

 ing years with unusually high precipitation are scattered, 

 1858, 1865, 1866, 1868, 1876, 1892 and 1905. 



Examining the annual figures for temperature, the an- 

 nual means, a remarkably harmonious series is discovered. 

 For the whole period of sixty-two years the greatest differ- 

 ence, that between the maximum and the minimum annual 

 mean, is only 8 degrees. The winters of 1879, 1881, 1883- 

 1888 inclusive were unusually cold, but the remaining sea- 

 sons of these years presented nothing abnormal in the way 

 of average monthly seasonal temperatures. Unusually low 

 precipitation followed for the summers of the years 1883. 

 1886, 1887 and 1888, while the spring of the year 1887 also 

 had unusually low precipitation. It is about this period 

 that the damage to native vegetation, so often referred to 



