THE PREGLACIAL DRAINAGE OF OHIO. 66 



hereafter. About one mile south of Alpha the valley again 

 contracts, ihere haviui? a width of perhaps one-tenth of a mile. 

 At this point the valley lies about 75 feet below the top of the 

 blufifs which are steep and composed of rock. Two miles farther 

 down, the valley has again expanded and has a width of 

 one-half mile. From the latter point to Bellbrook there are 

 several variations in the width of the valley. iThese result 

 largely from the entrance of tributaries and in part from the 

 irregularities in the deposits of drift, and perhaps also from varia- 

 tions in the durability of the rock. 



Just east of Bellbrook and north of the point at which the 

 Miami turns abruptly to the east, there is a marked change in the 

 width of the valley. Here the rock blufifs extend so close to the 

 river that the flood plain on one side is only 85 yards wide, 

 while on the opposite side there is scarcely room for a wagon 

 road. A cross section of the valley here is shown in the follow- 

 ing figure. 



//$?/ Cros5 Section of Miami at Col Jusf above 

 mouth of Sugar CreeK 



Of special interest is the terrace east of the stream. It is 

 in rock and has a pronounced slope up stream. From this point 

 the valley widens, rather slowly up stream and rapidly down. 

 The constriction in the valley and the expansion in both direc- 

 tions, the terrace sloping ///> stream, and the abrupt bend in 

 the river just below, make certain the existence of a col at this 

 place. 



At the point where the Miami bends sharply to the east it 

 is joined by Sugar creek which, though the smaller stream, flows 

 through the larger valley. While connecting these two streams 

 one mile north of this place there is an abandoned valley. The 

 followins: sketch will indicate these relations. 



