144 GEORGE C. MATS ON 



VI and Map II, C) on the south side of the north ridge, points 

 strongly toward the existence of a channel beneath the ridge. 



Nature and size of chaiinels. — The fact that the rock rises per- 

 pendicularly above each of these channels indicates that they are 

 gorges, and the rock in each of the ridges forms a rock island. 

 The postglacial gorge is 25 yards wide, 50 yards long, and 90 

 feet deep. The gorge south of the southern ridge is over 250 

 yards wide and lOO feet deep. The drift has been removed 

 down to 910 feet A. T. without exposing the rock bottom. The 

 gorge (Z^) just south of the house is 35 yards wide and 90 feet 

 deep. It has its bottom at 910 feet A. T. This is at the same 

 time level as the bottom of the postglacial gorge. The gorge 

 running east from the house is 125 yards wide and 1 10 feet deep. 

 Its bottom, as indicated by borings near the house and between 

 the rock in the two ridges, is below 890 feet A. T. The gorge 

 just south of the reservoir is more than 175 yards wide and it has 

 been cut to 880 feet A. T. without encountering rock. This 

 would give it a depth of 120 feet. The gorge between the mid- 

 dle and northern rock islands, is 125 yards wide and has a drift 

 bottom 900 feet A. T. The outcrop along the stream at the east 

 end of this gorge, is an extension of the rock in the northern 

 ridge and it was probably originally at the same height, having 

 been lowered by the swinging of the stream against it. It now 

 stands 905 feet A. T. 



The arrangement of the sections of gorges into a series of 

 continuous gorges depends upon size, depth, and position. Gorge 

 No. I ' passes beneath the southern ridge, east of the middle 

 ridge, and east of the rock in the northern ridge. From the 

 slope of the rock-floor of the broad valley, as indicated by well 

 records and rock outcrops, this channel must lie approximately 

 in the axis of the broad valley of Ten Mile Creek, already 

 described. Gorge No. 2 passes beneath the southern ridge, 

 westward past the house, beneath the middle ridge, and west of 

 the northern ridge. That this gorge could not pass between the 

 middle and northern ridges is shown by the fact that its bottom 



' The numbering is for convenience only, and does not indicate the supposed 

 chronological order of formation. 



