iS6 GEOLOGi. 



the same course with the plane of its lamina, 

 which dips something less than a degree to the 

 north-west. The edge of this calcareous sheet is 

 visible for more than half a mile, projecting gene- 

 rally two or three feet out of the schistic ledge to 

 the place of its descent below the surface of the 

 lake ; and there it is seen uncovered for some dis- 

 tance, and extending into the lake more than a 

 quarter of'a mile, to the termination of the slate 

 rock, and to the place where the water becomes 

 very deep. When this lime stone lay above the 

 surface of the lake, the action of the water has 

 worn awa}' the subjacent slate, and the calcareous 

 blocks fell off; but as these blocks are much 

 harder than the schistic, they are of course a long- 

 er time io wearing away. Thry are however 

 found extending from the ledge many rods into 

 the lake, and in a state of gradual diminution, the 

 outer sides being ground down to pebbles. These 

 appearances exist in other places, and warrant 

 ihe conclusion, that this schistic barrier once ex- 

 tended very far into the lake. 



While the south shore ofLake Erie is surround- 

 ed by schistic, that of Lake Ontario is supported 

 by lime and sand stone, much harder substances. 



These intimations are certainly deserving of 

 a inore critical examination, and since I am on 

 the subject of geology, I shall exhibit to you an 



