HYDROLOGY OF NEW YORK 



315 



exact to justify the labor of preparing a tabulation of ibis 

 character. 1 



Referring to the tabulation on page 31.1, it is learned that the 

 rainfall in that portion of the basin of the Great Lakes tributary 

 to Niagara river was, for 1SG8, 523,420 cubic feet per second, and 

 the evaporation from the water surface of the lakes tributary to 

 Niagara river was 101,890 cubic feet per second. Hence the 

 evaporation from the lake surfaces was nearly 20 per cent of the 

 rainfall on the whole basin. Assuming for the moment the truth 

 of these figures, we have 80 per cent of the total rainfall from 

 which the land evaporation must be deducted before anything can 

 run off. Again assuming the land evaporation at 1.70 feet, there 

 results a loss from this source alone of 298,000 cubic feet per 

 second; adding to this the evaporation loss from the water sur- 

 faces gives a total evaporation loss of 399,890 cubic feet per 

 second. The runoff is the difference between rainfall and total 

 evaporation losses. If. therefore, the land evaporation was 1.7 

 feet for the year 1B68, the runoff (would have been in reality only 



i There have been a number of independent measurements of volume of the 

 Niagara, and though the results differ widely, they probably do not differ 

 more than the actual volume of the river at various stages of Lake Erie. 



Lyell (1841 ?) cpiotes Ruggles as authority for a volume of 250,000 cubic 

 feet per second. 



E. R. Blackwell, computed by Allen (Am. Jour. Sci., 1841), obtains 374,000 

 cubic feet per second. His work was afterwards recomputed by D. F. 

 Henry, who obtained 244,797 cubic feet per second. 



In the Annual Report of the Chief of Engineers, United States Army, 

 for 1867-68. D. P. Henry gives as a result of observations in August and 

 September. 1867. 242,494 cubic feet per second. A year later he recom- 

 puted from the same data, and obtained 240,192 cubic feet per second. lie 

 also made a new measurement by a different method (see report for 1868- 

 09) from which he obtained two results, 304,307 and 258,586 cubic feet per 

 second. 



TV. P. Reynolds (Annual Report of the Chief of Engineers. United States 

 Army, 1870?), gives the result of observations from June to September. 

 1869, 212,860 cubic feet per second. . 



In the Annual Report of the Chief of Engineers. United States Army, for 

 1S71, there is a mention of a result, without date of measurement, 245,296 

 cubic feet per second. 



In the Annual Report of the Chief of Engineers, United States Army, for 

 1891-92, Quintus, as a result of gaging, gives the volume, reduced to mean 

 stage, as 232,800 cubic feet per second. 



Sir Casimir S. Gzowski, from continuous observations at the Inter- 

 national bridge, 1S70-1873, gives an average discharge for that period of 

 246,000 cubic feet per second. 



