(Slacfal anD ipreglacial ftafces, 225 



whole face of the country over which the ice 

 drifted. 



The glaciated region of North America is 

 among the most productive in the world, and 

 in many respects presents a most pleasing 

 landscape. 



Other lakes besides these mentioned have 

 been formed during the ice period through 

 blocking the course of a river by the ice itself. 

 Dr. Wright, during the time he traced out the 

 line of the terminal moraine, discovered that 

 the ice sheet crossed the Ohio Kiver at a point 

 near Cincinnati, where there is a great bend 

 to the northward in the river. With the ex- 

 ception of this point and perhaps another 

 point below, the edge of the great ice sheet 

 kept a little north of the Ohio Kiver. At this 

 point, however, the ice seems to have filled the 

 valley from hill to hill, which very naturally 

 would form a great dam or lake in the Ohio 

 Valley. Of course such a lake could not be 

 permanent, because, when the ice melted away, 

 it again opened the channel and allowed the 

 water to flow off. 



Some years before this discovery was made 

 there were terraces found along the banks of 

 the Ohio Eiver and its tributaries that had 

 been the subject of much speculation. It is 

 well known that by the action of water from 

 rainfall, earth, gravel, and other debris will 

 wash down the side of a hill or mountain until 



