152 



GEOLOGY. 



Fig. 138, — Figure showing crenate river bank, the reentrants being determined by 

 joints. Dells of the Wisconsin River, near Kilbourn, Wis. (Atwood.) 



Fig. 139. — Lone Rock. An island isolated by the notable widening of a series of 

 joints. The joints in the rock of the island have themselves been so widened that 

 a rowboat may be taken through it in two directions. Lower Dells of the Wisconsin. 

 (Meyers.) 



