THE OHIO AND MONONGAHELA RIVERS, iti 



along the waters of the Ohio, where we find the same gravel, we find tl 

 debris of northern rocks at almost the same level. The- gravels take the 



slope of the river, so that we find them at 300 feet above tide at Hickman 

 and reaching up to 700 feet above the sea further up the river ; and they are 

 covered all the way, with very Blight interruptions, with the silt formation, 

 which may be traced almost to the very head-waters of the stream, partak- 

 ing of the character of the rocks of the several water-courses. The silt 

 formation is sometimes a loam, and I believe it is traceable all the way down 

 to the loess covering the Orange Sand deposits of the lower Mississippi 

 valley. 



Mr. F. J. H. Merrill: I should like to say a few words in regard to the 

 interglacial deposits of the Delaware. The region south of the moral 

 near Belvidere has been discussed as a type area. There is a here a broad 

 plain, over 200 feet above the river, which is covered with loam, and under- 

 neath which is a certain amount of gravel ; this comes up to the margin 

 of the moraine at about 460 feet above tide and about 260 feet above the 

 river. There are evidences of moraines, and there are also small gravel 

 deposits indicating that a body of water stood on the southwestern margin 

 of the moraine, and that this great plain along the Delaware river and val- 

 ley was filled with a body of water, either a lake or an estuary. I want to 

 ask President Chamberlin how, in a valley which has been filled with water 

 subsequent to the formation of the moraine, we are to di- . ish glacial 

 material that might have been deposited in the water that filled the valley 

 from any glacial material that might have been laid down in that valley 

 before the moraine came into existence? There are evidences that this val- 

 ley of the Delaware at the southwestern margin of the moraine was filled 

 with water to a height of about 460 feet above tide; and I am anxious to 

 know if there is any test by which the later glacial deposit can be differen- 

 tiated from the earlier one under the conditions I have mentioned. 



Professor I. C. White : The facts presented by President Chamberlin from 

 the valley of the Ohio have always been interpreted differently by other geol- 

 ogies who have studied that region. There is everywhere along the vail' - 

 of the Monongahela and Ohio evidence of submergence, and the question 

 which has just been asked is very pertinent. How are we to discriminate, 

 or what test shall we employ by which we can recognize the difference be- 

 tween glacial material brought down by the water from these northern 

 moraines and distributed all along the valley and that brought down by the 

 ice ? Now, my observations in the. Monongahela valley have shown that 

 we have an area extending over hundreds of square miles covered with cla - 

 showing unquestionably that deposits were made in water. These clays 

 mantle the hills where the surface is not b - and they extend up 

 about 1,100 feet above the sea. I have during the present summer made a 



LXIII— Bru - :. Am., Vol. 1, I 



