428 H. L. FAIRCHILD — GLACIAL GENESEE LAKES. 



has excavated a canyon in the Niagara formation, with three cataracts, 

 rivaling the simihir phenomena at Portage. 



POSTGLACIAL CHAISNELS OF TRIBUTARY STREAMS. 



The larger streams tributar}^ to the Genesee river generally lie in their 

 ancient valleys. This statement needs qualification chiefly as relates to 

 the lower or northern part of the drainage area, where the topogTai)hical 

 relief is small and chiefly drumloidal. Tlie middle and upi)er sections 

 of the basin lie near the extreme limit of tlie ice invasion. The ice ero- 

 sion was here consequently of less duration and less effective than farther 

 northward, and the grosser topographic features were not materially 

 changed. The saliencies were somewhat pared down, or the surface par- 

 tially smoothed, with consideral)le filling of drift in the valleys. Tlie 

 heavier dams of drift, interfering with the resumption of the stream 

 drainage, were usually formed in the lateral valleys at their junction with 

 the main or river valley. As a consequence of this closing of the mouths 

 of the side valleys, lateral local lakes were ])roduced, and the outlet or 

 waste-weir was frequently over the rock-wall of the old valley slo])e, the 

 morainic filling being usually higher in the middle of the valley. The 

 final result has been the making of postglacial rock-ravines near the 

 embouchure of several streams tributary to the river in the same manner 

 as the formation of the head of the Portage canyon. 



One of the largest of these rock-cuts in lateral valleys is near the mouth 

 of Caneadea creek, upon the west side of the river. An immense moraine 

 and kame deposit blocks the side valley, and tlie consequent local mo- 

 rainal lake was drained b}^ the outlet cutting down through rock upon 

 the south side of the dam. 



A very typical and interesting example of iM)stglacial rock-cutting is 

 seen at Angelica. The short rock-ravine, over 100 feet deep, in the course 

 of Angelica creek has been formed upon the northwest side of the ancient 

 valley. This moraine dam, which was a distinct ridge across tlic valley, 

 consisted of unenduring material, and has l)een so far removed, ajjpar- 

 ently by atmos[)heric agencies, that now it is not nearly so high as the 

 top of the rock- cut. 



Other postglacial rock-cuts in the course of direct tributaries of the 

 river occur in the channels of Silver lake outlet, Wolf creek, Canaseraga 

 creek, \yisco3^ creek. Cold creek. Black creek. White creek. Van Campens 

 creek, Phillips creek, Vandemark creek. Knight creek, Chenunda creek, 

 and probal)ly maii}^ others ; also in the west and middle branches of the 

 river. 



In the indirect or secondary tributaries of the river rock-cuts are doubt- 

 less numerous, not counting those of stream channels which are wholly 



