HYDROLOGY OF NEW YORK 793 



tion of uniform distribution of lockages, there must necessarily be 

 considerable waste. Taking into account the actual water-surface 

 area of the summit level of (71,900 x 334)= 24,014,600 square feet, 

 and assuming an inflow of 1300 cubic feet per second, without any 

 outflow, the increase in depth per hour becomes 0.19 foot, or in 

 three hours the increase in depth would become 0.58 foot. How- 

 ever, if there were no lockages for three hours, the depth would 

 not increase as rapidly as this because of the leakage at gates and 

 sluices and wastage on the spillways. In order to illustrate this 

 matter we may consider the following tabulation, in which the 

 heads are given in inches and feet. The coefficient used for the 

 computation, as derived from Bazin's experiments, is applicable 

 to a flat-crested, or nearly flat-crested, weir from 6 to 7 feet wide. 

 The quantity of discharge, Q, in cubic feet per second, is given per 

 linear foot of crest and also for 2500 feet of crest. 



Q per linear foot Q for 2500 feet 



of crest, in of crest, in 



Head cubic feet per cubic feet 



Inches Feet Coefficient second per second 



1 0.083 2.20 0.053 133 



2 0.167 2.20 0.150 375 



3 0.250 2.35 0.291 735 



4 0.330 2.42 0.459 1,148 



5 0.417 2.47 0.665 1.663 



It appears from the foregoing that when the water rises to a 

 depth of only one inch on such a crest, the discharge over 2500 

 linear feet would become 133 cubic feet per second, while for 

 two inches depth it becomes 375 cubic feet per second, and for 

 three inches depth, 735 cubic feet per second, and so on up to 

 1663 cubic feet per second for a depth of five inches. However, 

 the wastage would be less than these figures indicate, because 

 of the outflow from leakage and the wastage over the crest. 

 Under the existing conditions of the proposed deep waterways 

 summit level, whenever there is an interval of two or three 

 hours without lockages the wastage over the long spillways at 

 the ends of the level will amount to several hundred cubic feet 

 per second. This quantity may probably be reduced somewhat by 

 the use of flashboards, to be set in place and taken off as neces- 

 sary, although, in view of the sudden flood rises of the Mohawk 

 river and consequent necessity for removing the flashboards fre- 

 quently, the writer considers that such remedy would be some- 

 what unsatisfactory. The safer way. without doubt, is to provide 

 a liberal wastage requirement. On this basis, from 150 to 250 



