STBI^E WITHIN LIMITS OF SHELBYVILLE MOKAINE. 417 



many rods in length. A photograph of an exposure made in the diversion 

 channel of the Des Plaines is here furnished through the kindness of the 



Fig. 3.— Grooves exposed by canal in bed of Chicago Outlet near Lemont, Illinois, apparently duo to abrasion by 

 pebbles transported by water in the outlet rather than to glaciation. [Drawing from a photograph by Chicago Drainage 

 Commission.] 



Chicago Drainage Commission (see fig. 3). These channels were announced 

 in the Chicago newspapers to be glacial grooves, but they are apparently 

 due to water abrasion rather than glacial scoring. 

 mon xxxviii 27 



