OUT WASH FROM THE OLDEST DRIFT. 251 



north of Tomlinson Run. It stands about 300 feet above the river and 

 occupies an area of perhaps one-fourth of a square mile. On its surface 

 only a few waterworn pebbles were found, there being no continuous bed 

 of gravel. 



South of Tomlinson Run there are two terraces; the upper, a narrow 

 one, stands about 300 feet above the river and carries only scattering 

 pebbles; the lower, a broad shelf, stands about 200 feet above the river 

 and carries a deposit of gravel several feet in depth. In a gully in this 

 gravel a large number of clam shells were found which seem to have been 

 embedded with the gravel. As the gravel has probably been derived from 

 higher rock shelves and redeposited during the process of excavation, these 

 shells may be considerably younger than the old drift. As indicated on 

 page 94, the valley may not have been opened to the level of this lower 

 shelf until after the deposition of the gravel. 



At a cemetery in a recess of the valley back of Toronto, Ohio, a bed 

 of gravel was found at an altitude about 320 feet above the river, or 950 

 feet above tide, which contains occasional Canadian rocks. In a search 

 of half an hour 8 pebbles of granite and quartzite were found, which 

 represent all that occur in a collection of perhaps 10,000 pebbles. They 

 range in size from one-half inch up to 3 inches in diameter. The deposit 

 has a depth of 1.0 to 12 feet. A shelf of similar altitude appears opposite 

 Toronto, but it carries only scattering pebbles. 



Below Toronto scattering pebbles have been found on rock shelves at 

 numerous points at levels 200 to 300 feet or more above the stream, but 

 no bed of glacial gravel has been observed. On some of the shelves that 

 stand 200 to 250 feet ubove the river appear occasional Canadian rocks, 

 which are thought to have been lodged on these shelves during the excava- 

 tion that followed the gravel deposition. The features of the Ohio Valley 

 below the point where well-defined beds of glacial gravel occur are dis-. 

 cussed in Chapter III (see pp. 91-93, 108-109). We may, therefore, pass 

 to the consideration of glacial outwash in the Beaver Valley. 



BEAVER VALLEY. 



Only the lower 10 miles of the Beaver Valley lies outside the limits 

 of the Wisconsin drift, the border of that drift being near Homewood. 

 From the Wisconsin drift border southward to Beaver Falls there is a 

 broad rock shelf standing about 875 to 900 feet above tide, or 210 to 235 



