158 GEOLOGICAL SURVEY OF NEW JERSEY. 



Little Falls, while in the case of the Raritan it is due to the 

 dam itself and other artificial obstructions. In the figures next 

 given for the Passaic at Two Bridges and Raritan at Bound 

 Brook, this is corrected, the Passaic figures being also corrected 

 to allow for water stored in lakes and reservoirs, and we have 

 the rate at which the water came in immediately above the 

 point of restriction. These two, together with the Pompton, 

 represent catchments large enough to be free from local and 

 accidental features. The discharge by periods does not show 

 any effect traceable to forest conditions, indeed, the rapidity of 

 discharge is somewhat greater on the well-forested Pompton 

 catchment, and the figures are nowhere higher than for the 

 well-forested Pequannock. In general the discharge in inches 

 of depth for the first day will be greater as the catchment 

 decreases. This law is well exhibited in the 24-hour period. 

 Taking the whole 72 hours the volume of flood-discharge is seen 

 to vary materially on different catchments. This may be due 

 to local differences in the amount of rain or snow, or in the 

 absorbent power of the soil. It does not appear to be less on the 

 forested catchments. In order to eliminate the effect of differ- 

 ing volume of total discharge the second table is made up to 

 show what percentage of the total was discharged during the 

 first and second 1 2-hour periods and during the three 24-hour 

 periods from the beginning. In these tables the agreement 

 between the forested Passaic and deforested Raritan catchments 

 is striking. The Pompton, being a smaller catchment, naturally 

 shows a little higher rate for the first 12 hours. But it is about 

 four per cent, less during the first 24 hours, this four per cent, 

 having been carried over and discharged during the third day. 

 We are of the opinion that this slight retardation is attributable 

 to the lakes and ponds entirely. That it is not due to the high 

 percentage of forest seems proven from the fact that on the 

 Ramapo, one of the branches of the Pompton having about 'the 

 same percentage of forest, the retardation is considerably greater 

 than on the Pompton. Lakes and ponds operate also in the case 

 of the Rockaway to produce a similar result. The South Branch 

 of the Raritan shows a more rapid discharge than the foregoing 

 streams, but less rapid than the much better forested Pequan- 

 nock and Musconetcong, showing clearly that the difference is 



