HYDROLOGY OF NEW YORK 



341 



mean animal rainfall at Oxford for the same period was 27.30 

 inches, and the mean annual temperature, 48.5° Fahr. We have, 

 therefore, 3.54 inches less mean annual evaporation, as measured 

 in the catchment of the Thames, than at Hemlock lake. 



During the ten-year period, 1S93-1902, inclusive, the mean run- 

 oft' of the river Thamas was only 7.29 inches, instead of 8.49 

 inches, as in the previous ten-year period. In consideration of 

 the showing made of the low runoffs of streams in the State of 

 New York, it is probable that when a complete computation of 

 the runoff of Hemlock lake is made, it will be found to be some- 

 what less than that of the Thames in England. 1 



Geologically the Hemlock lake catchment is in the Hamilton 

 and Marcellus shale, with the hills at the sides rising to the rocks 

 of the Portage group. 



Discharge measurements of Oswego river. The following record 

 of Oswego river is taken daily, with the exception of Sundays and 

 holidays. 



These gagings are made at the State dam, three miles from 

 Lake Ontario, with an effective head at the dam of about 32 feet. 

 This dam is of masonry, with its crest 365.5 feet long. Flash- 

 boards are maintained during the greater part of the year. In 

 estimating the flow, when flashboards are removed, a discharge 

 curve has been prepared using coefficients in the weir formula, 

 as per Cornell experiment No. 3, given in the paper On the Flow 

 of Water Over Dams. 



It is possible that the records are somewhat too small, owing 

 to leakage and settlement of the dam. A headrace sup- 

 plies water to an electric-light plant and the Oswego water works 

 pumping station. There are eight water wheels in use. The 

 amount of water passed through these wheels varies from 300 

 cubic feet per second to about 650 cubic feet per second. In the 



i Discussion of the flow of the river Thames from 1883-1892. may be 

 found in (1) the Report on the Flow of the Thames, by A. R. Binnie, 

 Chief Engineer to the London County Council— a publication of the Coun- 

 cil, 1892; and (2) a Report on tbe Shrinkage of the Thames and Lea, by 

 Maurice Fitz Maurice, Chief Engineer — .a publication of the London 

 County Council, presented to tbe Water Committee on February 10, 1903. 



