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NEW YORK STATE MUSEUM 



of water stored. Probably at the present time they will cost some- 

 what more, but for water storage merely they will not exceed $75 

 or f 80 per million cubic feet. On the Mohawk and its tributaries 

 conditions are much, less favorable. Reservoirs there are likely 

 to cost from $200 to |300 per million cubic feet. Hence, as a 

 financial proposition, the Hudson river above Mechanicville is 

 likely to be more thoroughly regulated than the Mohawk river and 

 its tributaries, the more specially since water storage has not 

 only value here for preventing floods, but is also of considerable 

 value for water power. The same is true on the Mohawk river, 

 but the limit of cost of water power in comparison with steam 

 power will be much sooner reached on this stream than on the 

 upper Hudson. Since this phase of the subject is extensively dis- 

 cussed in the first report on the upper Hudson storage, it is merely 

 referred to here. 



Floods inCroton river. The catchment of the Croton river consists 

 of a broken, hilly country with its surface soil composed princi- 

 pally of sand and gravel. Clay, hardpan and peat, while found 

 in a few localities, are for the whole area only present to a limited 

 extent. The rock formation consists generally of gneiss, although 

 strata of limestone, some micaceous and talcose slates, with veins 

 of granite, serpentine and iron ore, occur in a few places. The 

 catchment area is about 339 square miles, above the old Croton 

 dam, at which point daily gagings of the stream have been taken 

 since 1807. According to J. J. R. Croes there is a well-attested 

 case of a maximum flood of 25,376 cubic feet per second, or 74.9 

 cubic feer per second per square mile. In reference to these figures 

 it may be remarked that probably they have been obtained by 

 the use of Francis's formula. The profile of the old Croton dam, 

 however, shows a rounded crest which, according to Bazin's co- 

 efficient, series No. 193, would give, with about 5 feet depth on the 

 crest, a discharge from 37 to 3S per cent higher than Francis's 

 formula. The maximum flood of the Croton may, therefore, be 

 from 30,000 to 35,000 cubic feet per second, or possibly as high as 

 cubic feet per second per square mile. 

 January 7-8, 1841, a severe flood occurred which washed away 

 i he earthen bank of Croton dam. At that time the ground was 

 covered with eighteen inches 6f snow, and rain falling continu- 

 ously for forty-eight hours, with high temperature, produced a 

 serious flood. The overflow weir was insufficient (o discharge the 



