BLANCHARD OR DEFIANCE MORAINE. 617 



ridges and knolls and why the gaps exist are interesting questions which 

 afford room for speculative inquiry but which are not well enough under- 

 stood at present to warrant the rendering of an opinion. 



THE OLD VALLEY OF ROCKY RIVER. 



The changes of drainage • in this region, especially in the plane 

 portion of it, have been sucli that several of the streams are in channels 

 entirely postglacial, draining territory whose preglacial di'ainage lines are 

 completely filled with drift. In one conspicuous instance, however, the 

 preglacial course has been abandoned, but not concealed, viz., that of the 

 East Foi'k of Rocky River. The fact was announced by Newberry^ that 

 the present mouth of Rocky River does not coincide with its ancient mouth, , 

 but comes to the lake shore 2 miles east of it. The river, however, touches 

 its old channel 2 miles above its mouth, one bluff being composed of rock 

 while the other is composed of till. A few years after Newberry's reports 

 were published. Dr. D. T. Gould, of Berea, Ohio, discovered that the old 

 course of the East Fork of Rocky River may be traced from the point 

 where Newberry left it (2 miles above the mouth of Rocky River), south- 

 ward into Strongsville Township, Cuyahoga County, where it becomes 

 coincident with the present course and continues so to the head of the 

 stream. The present course of the stream is nearly parallel with the 

 ancient one throughout this distance (about 15 miles), lying 1 to 1^ miles 

 west of it. The old course is indicated superficially by a shallow, trough- 

 like depression, about one-half mile wide and 10 to 40 feet deep, and its 

 existence is confirmed by borings which show that no rock lies near the 

 surface of this depression. The deepest boring (one near the Big Four 

 Railroad) is reported by Gould to have penetrated about 200 feet of drift 

 .before reaching rock, showing the rock floor to be nearly as low as the 

 surface of Lake Erie. 



Along the ancient course, from the vicinity of Berea southward for 

 nearly 15 miles, the Berea grit is wanting for a space of 1 to 1^ nnles or 

 more, while along the present stream throughout that distance the bed and 

 bluffs are composed of this formation. The present valley is a narrow 

 gorge but a few rods in width, while the ancient one has a width of a mile 

 or more. 



iSee Geology of Ohio, Vol-. 1, 1873, pp. 171-172; Vol. 11, 1S75, p. 16. 



