246 SKETCHES OF CREATION. 



the region was essentially the same as now. If, in an in- 

 terval of twenty or even of ten thousand years, little per- 

 ceptible change has taken place in the populations of the 

 globe, how vast a period must have elapsed during the 

 progress of organic mutations which have twenty times re- 

 sulted in the almost complete extinction of existing forms, 

 and their replacement by beings of other types ! 



I said that the level of Lake Erie was once at the top of 

 the heights of Lewiston, thirty-eight feet above its present 

 altitude. This elevation submerged the flats to the east 

 and west of the Detroit and St. Clair Rivers, and united 

 Lake Erie with Lake Huron by a shallow expanse of water, 

 which in some-places possessed a breadth of fifty miles or 

 more. Still farther, the level of Lakes Huron and Michigan 

 was raised twenty-five feet above their present altitude, 

 and a portion of the waters of the upper lakes found an 

 outlet from Lake Michigan into the Des Plaines River, and 

 thence into the Illinois and the Mississippi— if, indeed, a 

 large portion of the prairie region of Illinois was not sub- 

 merged by such an altitude of the lakes. At the same 

 time, Saginaw Bay of Lake Huron stretched into the centre 

 of the peninsula of Michigan. 



This is not the highest altitude at which the waters of 

 the lakes have stood, though the barriers which dammed 

 them have long since disappeared. Along the southern 

 borders of Lakes Erie and Ontario, the rocks arise from 

 their more southern depressions, and face the lakes in bold 

 escarpments three hundred and fifty feet above the respect- 

 ive levels of the waters. These bluffs have been the rocky 

 shores of the lower lakes. For unnumbered ages the furi- 

 ous north wind has rolled mad waves against those ada- 

 mantine walls, and battlement after battlement has tum- 

 bled down and been ground to powder by the tireless beat- 

 ing of the stormy surge. Between the foot of the mural 



