SUMMER IN A BOG. 47 



"Three miles is considered by one autbority 

 as a moderate estimate. A possible eighteen 

 for some regions is hinted at. I am more than 

 delighted to hear the Professor's theories in 

 regard to this portion of the country." 



"In this part of Ohio," proceeded the Pro- 

 fessor, "there were two ice invasions — ^that of 

 the lUinoisan ice-sheet; and the last invasion, 

 that of the Wisconsin drift. Between the two 

 was an inter-glacial period in which the ice- 

 sheet melted back probably from all of Ohio 

 and southern Canada, and possibly disappeared 

 from North America wholly — ^no one knows. ' ' 



"I am not altogether ignorant of what you 

 are speaking. Professor," said Mrs. Wier ; "but 

 there are several other 'invasions' mentioned 

 in my son's text-books, into which I glance as 

 I find time. ' ' 



"The evidence for the three earlier ice- 

 advances is not found in Ohio, but farther west. 

 If the earlier sheets invaded Ohio, the later 

 advances (lUinoisan and Wisconsin) destroyed 

 their deposits and prevented our knowing of 

 them." 



As the Professor concluded we came to the 

 end of the private road upon which we had been 

 walking. A gate opened on the highway, and 

 here I should leave them, I thought regret- 

 fully, to find my way to the next mterurban 



