GLACIAL DAMS, LAKES AXD WATERFALLS. 391 



Since the above account was written there has been a 

 very animated discussion of the theory, the result of which 

 has been to confirm the general view here maintained, while 

 modifying some of the subsidiary points. Professor T. C. 

 Chamberlin early expressed his disbelief in the dam. and 

 after traversing the Monongahela Yalle}' from Morgantown 

 to Pittsburg expressed his belief that the clay deposits there, 

 which Professor I. C. White had regarded as practical]}' on 

 a water level for a distance of more than 100 miles, were flood 

 plain deposits of a flowing stream descending with the gradient 

 of the valley. As Professor Chamberlin had taken pains to 

 express this view in his introduction to my Bulletin published 

 by the U. S. Geological Survey (No. 54), it became necessarj^ 

 for a committee of the American Association for the Advance- 

 ment of Science to go over the ground with Professor White. 

 The result was that everyone was convinced of the correctness 

 of the facts as stated in my original publication.* It appeared 

 that as Professor Chamberlin did not find Professor White 

 at home, he failed to see the facts which Professor White had 

 recorded. That an ice dam existed which ponded up the water 

 in the Monongahela to a height of more than 1,000 feet above 

 the sea is established beyond all controversy'. But its immedi- 

 ate connection with the Cincinnati ice dam is now thrown 

 into the background by the broader considerations already 

 brought to light in discussing the formation of the present 

 Ohio River. 



The following facts detailed in a paper read, by Professor 

 White, before the Geological Society of America, f at the Buf- 

 falo meeting in 1896 are as interesting as they are conclusive 

 in establishing the existence of an ice-dam in the Upper Ohio 

 Valley. At three different points the divide between the Up- 

 per Monongahela basin and the valley of the Ohio, is cut by 



* 'Bulletin of the Geological Society of America," vol xiv (1902), 

 p. 4. 



t Published in "Am. Geol.," vol. xviii, Dec. 1896, "Origin of the 

 High Terrace Deposits of the Monongahela River." 



