7 



to impalpable dust, in the crushing, grinding mill of glacial 

 action, as few pieces of wood are ever found among the bones 

 of glacial remains. 



Under the great weight of ten thousand feet of ice extend- 

 ing over a wide territory, the crust of the earth began to settle, 

 and depression to the extent of from twelve to fifteen hundred 

 feet below the present level was attained, and known as the 

 Champlain epoch. A consequent milder climate prevailed, 

 and the ice sheet began to withdraw to more northern latitudes, 

 leaving its load of earthy material strewn over the surface the 

 ice mass had formerly covered. The recession was slow and 

 interrupted, being for short periods stationary, laying down 

 our intermoraineic ridges and broken ranges of hills. The 

 withdrawal continued until the border of the ice sheet lay north 

 of the great lakes. Whether it receded sufficiently far north 

 at this time to unlock the ice bound St. Lawrence, and re-estab- 

 lish drainage to the northeast is not known. The melting of 

 this mountain of ice produced great floods and mighty streams, 

 all pouring their waters to the south, as the St. Lawrence, the 

 natural outlet of these waters was frozen solid and overlain by 

 thousands of feet of glacial ice. The waters were carried to the 

 south through our locality, by four great channels, the Ohio, 

 Wabash, Kankakee, and the Desplaines. These at the zenith 

 of their fullness were mighty streams, any one of which was 

 much larger than the Mississippi of to-day. And these, with 

 its western tributaries, gave the Mississippi its great flood 

 plain of thirty miles in breadth. Whether the withdrawal of 

 the ice sheet to the north of the lakes was followed by a long 

 period of milder or tropical time, or, whether an advancement 

 to a point below the lakes immediately followed, is a question 

 strongly debated by eminent glacial scientists. Professor T. 

 C. Chamberlain who made a geological survey of the glaciated 

 territory of the United States, maintains that between the first 

 advance, which reached to the lower moraineic border, and the 

 last advance which extended to below the lakes, there was a 

 long period of time, accompanied by a warm tropical climate; 

 while other eminent glacial students contend that there was no 



