Plate 6 



The Karsten, showing effect of surface and ground water on Onon- 

 daga limestone. The water dissolves the rock along the joint planes 

 forming deep fissures which widen into caves in places. Some of these 

 fissures extend to a depth of ioo feet or more. On top of cliff at 

 Blue lake 



Outcrop of Marcellus shale showing the numerous joint planes and 

 the effect of the joint planes on the rapidity of weathering. The ex- 

 posure is on the bank of a brook which carries away the talus as it 

 is formed 



