1909.] THE CAYUGA LAKE BASIN, N. Y. 381 



The average precipitation for the Central Lake region is shghtly 

 less than that for either the Great Lake or Eastern Plateau. The 

 mean annual precipitation for these regions compiled from precipi- 

 tation data for the years 1891 to 1902 is: Great Lakes 35.65 inches, 

 Eastern Plateau 40.8 inches, Central Lakes 34.46 inches. The nor- 

 mal monthly precipitation at Ithaca compiled from the last twenty- 

 nine years follows : 



January 2.16 in. July 3.75 in. 



February 1.87 in. August 3.24 in. 



March 2.44 in. September 2.83 in. 



April 2.29 in. October 3.17 in. 



May 3.43 in. November 2.58 in. 



June 3.88 in. December 2.64 in. 



From 1900 to 1907 there have been from 150 to 185 rainy days 

 each year. For the same period the annual snowfall (unmelted) 

 has varied from 46.4 to 75.8 inches, the average being 63.6. One of 

 the striking features of the region about Ithaca is the small per- 

 centage of clear days, as the following table will show : 



Percentage of 

 Cloudy. Partly Cloudy. Clear. Clear Days. 



1900 174 109 82 22.4 



1901 171 126 68 18.6 



1902 149 151 6s 178 



1903 195 98 72 197 



1904 -. 180 115 71 194 



1905 148 126 91 24.9 



1906 164 92 109 29.8 



1907 163 140 62 16.9 



Based upon average hours of sunshine from 1900 to 1903 R. G. 

 Allen derived 49 per cent, as an annual mean of sunshine, or a 

 monthly mean of 189 hours of sunshine. 



The average of mean relative huinidities at Ithaca from 1900 to 



