SURFACE GEOLOGY. 



11 



later date, and the one by which the excavation of the lake basin was 

 principally effected. 



Map showing directions of glacial strise along the margin of the highlands 



in Northeastern Ohio. 



The broad ice-sheets which have existed outside of Ohio have left 

 their records in the nearly uniform and continuous glaciated surface 

 which covers so much of Canada, New England, New York, and the 

 States of the north-west. In nearly all parts of New England are traces 

 of an ancient ice-sheet which moved in a direction about south south- 

 east, and was of such thickness and magnitude as to override all the 

 features of the local topography, except Mt. "Washington. Hence the 



