1^4 dEOL^ev. 



LETTER XLV. 



Western Region, August^ 1820. 

 My Dear Sir, 



In a late letter 1 attempted to show that the 

 iand was continually gaining on the lakes, by the 

 agency of calcareous depositions, and I think ihat 

 Ipointed out a region of schistic formation, Iwsig 

 south of the great lime stone ledge of the west. 

 That this calcareous formation dips to the soiith, 

 I have no doubt, but whether it underlays the 

 schistic, 1 have not been able to ascertain. This 

 southern depression of the calcareous ledge below 

 the crumbling slate, would necessarily create ba- 

 sins for the springs and rains of the country, and 

 which by wearing away that fragile subsiancq, 

 would in time expand into lakes. This is evident- 

 ly the case with the Cayuga lake, which is con- 

 ■jinually enlarging its borders ; and the fall of old 

 Jedges from the precipices demonstrates that the 

 present order of things has not been of very re- 

 mote antiquity. 



The shores of Lake Erie are sustained by strata 

 ®f schistic which are continually giving way be- 

 fore the violence of the waves, and the whole lake 

 is supposed to be in a state of continual expansion. 



