GLACIAL EPOCH. 



549 



ten, fifty, one hundred, or even several hundred miles. In many cases 

 they must have been carried across valleys 1,000 or 2,000 feet deep, 

 and lodged high up on the mountain beyond. In many portions 

 of New England and about Lake Superior the number of fragments, 

 small and great, is so large as seriously to encumber the soil. Not only 

 the large bowlders, however, but the whole mass of the material we 

 have been describing, seem to have been shifted to a greater or less ex- 

 tent. It is for this reason that the material has been called Drift. 



Surface-Rock underlying* Drift. — On removing the drift-covering 

 the underlying rock is everywhere polished and planed and scored with 

 parallel lines (Fig. 928), and moutonne, precisely like rocks over which 

 a glacier has passed. We will, therefore, call this surface-appearance 

 " glaciation." We reproduce here from page 56 the roclies m'outonnees 

 of an ancient glacier in Colorado (Fig. 929). Examinations of the 



Fig. 929.— Roches Moutonnees of an Ancient Glacier, Colorado (after Hayden). 



scorings show that they often pass straight up inclines for considerable 

 distances, i. e., up one side of a hill, over the top, and down the other 

 side. Their direction is uninfluenced by smaller inequalities of surface, 

 though they are thus influenced by the great valleys and mountain- 

 ridges. 



The general direction of the scorings corresponds with that of 

 transportation of the bowlders, showing that they are due to the same 

 cause. Perfect soil on perfect sound rock always shows that the soil 

 has not been formed in situ, but has been shifted : the polishing, plan- 



