53° 



JOHN L. RICH 



in the valley and formed the stream bottom. If such were the case 

 we would expect to find no distinct channel after the ice had melted. 



At an elevation two hundred feet lower on the same hill, and almost 

 due southwest of the channel just described is another of the same 

 general type. It begins on the west slope of the hill as a shallow, 

 indistinct, slightly swampy channel with banks varying in height from 

 one to three feet. After continuing thus for about 150 feet it sud- 

 denly changes, at the site of an ancient waterfall, to a deep partly 

 rock-sided gorge which contours the hill for a distance of about one- 

 fourth mile. Its depth here is approximately forty feet. A short 

 distance east of the mouth of this channel is another shorter one cut 

 in the rock at the base of the hill. The two were probably contempo- 

 raneously formed by the same stream. 



Several features of this channel show that it was formed previous 

 to, or during the advance of the last ice-sheet, and that streams 

 associated with the retreating Wisconsin ice did little more than to 

 clear out a part of the debris with which the channel had been filled. 

 The lines of evidence pointing to this are : (i) the present V-shape of 

 the gorge, (2) the presence of considerable drift within the gorge, and 

 (3) the only occasional outcrop of rock in the gorge walls. The 

 bottom is not flat as would be expected if the gorge had been cut by 

 the last stream which flowed through it. The fiat portion of the 

 bottom is very narrow; only a fraction of the width of the gorge, and 

 in no part of the bottom is rock visible. 



This is one of two channels among the large number studied, in 

 which the sites of waterfalls were found. 



Wedgwood channel. — One and one-half miles west-southwest of 

 Wedgwood Station (No. i, Fig. 2, from Watkins sheet, U. S. G. S.) 

 is a marginal channel distinctly older than the final retreat of the last 

 ice-sheet. It is now largely drift-filled and shows no trace of the 

 presence of a stream since it was uncovered by the ice. It is not fiat 

 bottomed, as are the undisturbed channels, but has a decided V-shape, 

 East of the channel a small rock hill has been isolated by the channel 

 cutting. Rock is exposed in the walls in only a few places. One 

 exposure at X (Fig. 3) shows an approximately vertical rock wall 

 buried beneath the glacial drift which partially fills the gorge. A few 

 feet north of X the channel bottom rises several feet to a drift divide 



