222 THE ICE AGE IN NORTH AMERICA. 



the Pacific slope, the following, described by Mr. I. C. Rus- 

 sell, may serve as specimens : 



If one proceeds up the canon [of Leevining Kiver, Modo 

 county, California], he will cross five or six small terminal mo- 

 raines which traverse from side to side the broad trench left 

 by the ancient glacier. These are seldom more than fifteen or 

 twenty feet high, and are separated by grassy meadows. The 

 creek was formerly dammed by these moraines and forced to 

 expand so as to form small lakes ; but these have long since 

 been drained by the cutting of channels through the obstruc- 

 tions.* 



Other instances have been already mentioned in describ- 

 ing the glaciated boundary in Colorado, southern California, 

 Oregon, and the State of Washington. Moraines of retroces- 

 sion characterize almost every mountain valley which was 

 occupied by ice during the Glacial period. 



The distribution of till in North America has been the 

 subject of an immense amount of investigation during the 

 past few years, accounts of which will be found in the vari- 

 ous scientific journals and State reports. Most prominent of 

 all are those carried on by Mr. Frank Leverett, Professor 

 Geo. H. Stone, and Dr. Warren Upham of the United States 

 Geological Survey, and embodied in the monographs on the 

 " Glacial Formations and Drainage Features of the Erie and 

 Ohio Basins," "The Illinois Lobe," "The Michigan Glacial 

 Deposits" (by Leverett); "The History of Glacial Lake 

 Agassiz" (by Upham); and the "Glacial Deposits of Maine" 

 (by Stone). 



From these it appears that there are no less than twelve 

 moraines traceable across Ohio between Cincinnati and Lake 

 Erie, all belonging to the last, or so-called Wisconsin Episode; 

 these follow very irregular lines, and are not always easy of 

 recognition. Evidently they are moraines of recession, indi- 



*"Quaternary History of Mono Valley, California," p. 334. 



