132 NEW YORK STATE MUSEUM 



Comparison of evaporations, Hudson and genesee rivers 



Evaporation Evaporation 

 of Hudson of Genesee 

 lea1 ' area area Difference- 



1S90 21.79 26.32 —4.53: 



1891 .22.40 21.07 —1.67 



1892 20.79 26.27 —5.48 



1893 20.27 25.95 —5.68 



1894 22.00 28.41 —6.41 



1895 19.21 24.33 —5.12 



1896 21.58 27.88 —6.30 



1897 20.32 25.01 —4.69 



1898 20.65 27.37 —6.72 



Mean 21.00 26.18 —5.18 



It will be noticed that in the first of the two preceding tabula- 

 tions for the Hudson river, there are eleven years included and 

 that the average of the rainfall is 44.94 inches ; the average runoff 

 is 23.98 inches, and the average evaporation is 20.96 inches. The 

 Genesee river, on the contrary, only includes nine years, fvoiu 

 1890 to 1898, inclusive. 



In the second tabulation the years 1890-1898, inclusive, have been 

 taken for not only the Hudson river, but also for the Genesee, for 

 purposes of comparison. The taking of the Hudson river for 

 nine years instead of eleven makes a slight difference in the means. 

 The rainfall is 45.27 inches; the runoff, 24.27 inches, and the 

 evaporation, 21 inches. The Hudson river table is not worked 

 up to date, although the data are at hand, for the reason that the 

 Genesee river data do not extend beyond the year 1898. There is 

 no way. therefore, of comparing the two since that year. 1 



Variation in weir measurements. The writer has shown 2 the 

 considerable variation in weir measurements due to the difference 

 in form of weir alone. So great are these that any conclusions 

 based upon the data of sharp-crested weirs applied to other forms 



1 Partially abstracted from paper, Data of Stream Flow in Relation to 

 Forests, by Geo. W. Rafter. Lecture before engineering classes of Cor. 

 \'nl. Ap. 14, 1899. Trans. Assn. of Civ. Engrs. of Cor. Uni., Vol. VII, 1899. 



2 On the Flow of Water over Dams: Trans. Am. Soc. C. E., Vol. XLIV, 

 p. 220. 



