OUTWASH OF THE MIAMI LOBE. 377 



forming', the position of the inner member being- sixch that water from it 

 could not have been discharged down the -s'alley; and of the two periods 

 the earHer one seems to have fui-nished nearly all the glacial material to 

 the valley, the gdacial terraces leading into the valley being more numerous 

 and also more capacious frcim the outer than from the middle member. 



The Great Miami, above the mouth of Mad River, has a much nar- 

 rower valley than below, or than the valley of Mad River itself, the general 

 width being one-half mile or less. In the vicinity of Troy it is, for a few 

 miles, expanded to a width of a mile or more, and contains a gravel plain 

 standing about 20 feet above the river, on the borders of which there is a 

 terrace or remnant of a higher plain standing 30 to 35 feet above the river. 

 It is thought that this higher plain may have been connected with the ice 

 sheet at the time the inner member of this niorainic system was forming, but 

 the connection is not clearly established. The lower plain appears also to 

 be of glacial age, and apparently finds its head in the Union moraine, a few 

 miles above Piqua. A description of it is given in connection with that 

 moraine. 



Below the point where the outer member crosses the Great Miami 

 (near Carlisle) that stream flows through a gravel plain, 1 to 3 miles 

 wide, which, throughout much of its length, stands less than 50 feet above 

 the river, but which near the mouth attains a height of 100 feet abo^•e the 

 river owing to the more rapid descent of the present stream. Attention 

 was called on a preceding page to the presence of a buried soil beneath this 

 plain, a few miles below Hamilton, at a depth of about 60 feet. It is 

 thought that the valley received an average filling of at least that amount 

 at the time these moraines were forming, as a result of the overburdened 

 condition of the glacial floods. That the stream which deposited this mate- 

 rial was vigorous is shown by the coarseness of the deposit, the greater 

 part of the material being clean gravel, with a general freedom from silty 

 or fine material such as would have been deposited under slack-water 

 conditions. 



There is a small gravel apron along the outer border of the outer 

 member on the uplands east of the Great Miami, at an altitude about 200 

 feet above the river, which is crossed by the Springboro and Dayton pike 

 nearly due east of Miamisburg. It is situated in a narrow plane tract lying 

 between the moraine and some limestone ridg-es to the southeast, and forms 



