Foshay — Preglaoial Drainage of Western Pennsylvania. 399 



rivers to overflow to the south and cut down their divides. 

 They united to form the modern Allegheny River and thus we 

 have the phenomenon of reversed drainage in the upper Alle- 

 gheny region. The story of the Beaver valley is to be told 

 in much the same words, but Professor Carll — not having 

 examined the region — did not see as clearly as Professor 

 Spencer the former drainage of this part of the State. He 

 says,* "I strongly suspect that Big Beaver River is a glacial 

 enlargement of a small ancient stream formed in the same 

 manner as those found in the summit basins and that anterior 

 to the Ice Age the Shenango and other headwater streams of 

 the Beaver, including the Connoquenessing, delivered north- 

 wardly through the Mahoning and Grand Rivers into Lake 

 Erie basin. . . . ." If he had placed the ancient divide, cut 

 through during the Glacial Epoch, in the present Ohio valley 

 somewhere between the mouth of the Little Beaver and Wells- 

 burg, W. Ya., instead of placing it in the Beaver valley, he 

 would have been correct, as will be seen below. 



The evidence that Spencer River, whose bed is now buried 

 beneath many feet of drift materials, once flowed northwardly 

 is to be found in a very complete series of measurements of 

 the depth of the drift tilling taken from the records of oil and 

 gas wells drilled in the valleys during recent years. In the 

 table below I give only maximum depths at not too frequent 

 intervals but it must be understood that there is hardly a mile 

 of the distance covered in which there are not one or more 

 records showing the presence of the old channel. 





Dist. from 





Low Water. 



Depth of 



Old Floor. 





Pittsburgh. 



Place. 



A. T. 



Filling. 



A. T. 



1. 



o- 



Pittsburg. 



699 ft. 



44 ft. f 



655 ft. 



2. 



io- 



Coraopolis. 



? 



50 ft. 



? 



3. 



19- 



Aliquippa. 



677 ft. 



60 ft. 



617 ft. 



4. 



25"-2 



Beaver. 



670 ft. 



+ 60 it.% 



-610 ft. 



5. 



29-8 



Beaver Falls. 



700 ft. 



-flOOft.g 



-600 ft. 



6. 



46-8 



Lawrence June. 



760 ft. 



+ 150 ft.ff 



- 6 1 ft. 



7. 



51-4 



Edenburg. 



780 ft. 



200 ft. if 



580 ft. 



The figures in the fifth column of the table it will be seen 

 demonstrate a progressive deepening of the drift filling as we 

 go northward and when reduced to tide-level prove that the 

 old floor at present dips slightly to the north. 



* Report III, Sec. Geol. Survey Pa,, p! 392— footnote. 



f An. Rep. Pa. Survey 1886, Pt. II, p. 730. Jones & Laughlin, Nos. 1 and 2. 

 % Rep. Q, Pa. Survey, I. C. White, 1878, p. 14. 

 § Rep. Q, Pa. Survey, I. C. White, 1878, p. 15. 



|[ Rep. Q, Pa. Survey, I. C. White, 1878, p. 16, quoted from Dr. J. S. Newberry 

 in Geology of Ohio. 



IT Rep. QQ, Pa. Survey, I. C. White, 1879, pp. 19, 184, 202. 



