HYDROLOGY OF NEW YORK 



421 



The following statements in regard to these measurements are 

 abstracted from Mr Jervis's report i 1 From the Eaton brook results 

 it appears that the average runoff from June to December, 

 inclusive, was 39.2 per cent of the rainfall and from June to 

 October, inclusive, 31.9 per cent of the rainfall. The minimum 

 monthly runoff was in August, which shows only 19.2 per cent 

 of the rainfall. The rainfall in the month of June, 1835, on 

 Eaton brook was 6.72 inches and in July 2.74 inches. The per- 

 centage of runoff to rainfall for June was 35.8, whereas for July 

 it was 41.4, which would indicate that the bulk of the June rain 

 must have been at the end of the month. 



From the measurements of Madison brook it appears that in 

 1835 the average runoff for the whole year, including the snow on 

 the ground on January 1, was 44.9 per cent, or nearly one-half 

 of the rainfall. Mr Jervis points out that on account of the 

 storage of the reservoir, the Madison brook record can not be taken 

 for the summer months, but that the year should be divided into 

 two periods. For the first period he gives the results from Jan- 

 uary to May, inclusive, during which the runoff was 66.2 per 

 cent of the rainfall, and for the second from June to October, 

 during which the runoff was 24.6 per cent of the rainfall. During 

 the second period, June to October, inclusive, Eaton brook gave 

 a runoff of 31.9 per cent of the rainfall. Mr Jervis explains these 

 different results by the different characters of the two districts 

 drained. Eaton brook valley is narrow, the area drained steep, 

 with a close-textured soil. Madison brook valley, on the other 

 hand, is wider, with easy slopes, and the soil is more porous 

 than that on Eaton brook. Mr Jervis concludes his discussion 

 with the remark that Eaton brook valley would afford more than 



iFor Mr Jervis's original report see appendix F to Ann. Rept. Canal Com., 

 1835, Ass. Doc. No. 65, pp. 55-60. Mr Jervis's tables, with extracts from 

 the report are also quoted in the following documents: 



(1) Report of F. C. Mills, Chief Engineer Gen. Val. Can., in appendix D 

 to Ann. Rept. Can. Com., 1837, Ass. Doc. No. 80, p. 81. 



(2) Report of W. H. Talcott, Res. Eng. Gen. Val. Can., 1840, Ass. Doc. 

 No. 96, p. 51. 



(3) Report of the Regents of the University, 1838, Sen. Doc. No. 52, pp 

 208-211. 



(4) Documentary History of the New York State Canals by S. H. Sweet, 

 Dep. State Eng. and Sur., 1863, Ass. Doc. No. 8, pp. 203-204. 



