20 MAN AND THE GLACIAL PERIOD. 



level, one thousand feet thick, and four hundred and fifty 

 miles in length." 



A similar vertical wall of ice was seen by D'Urville, off 

 the coast of Adelie Land. He thus describes it : " Its ap- 

 pearance was astonishing. We perceived a cliff having a 

 uniform elevation of from one hundred to one hundred 

 and fifty feet, forming a long line extending off to the 

 west. . . . Thus for more than twelve hours we had fol- 

 lowed this wall of ice, and found its sides everywhere per- 

 fectly vertical and its summit horizontal. Not the small- 

 est irregularity, not the most inconsiderable elevation, 

 broke its uniformity for the twenty leagues of distance 

 which we followed it during the day, although we passed 

 it occasionally at a distance of only two or three miles, so 

 that we could make out with ease its smallest irregulari- 



Fig. 10.— Iceberg in the Antarctic Ocean. 



ties. Some large pieces of ice were lying along the side 

 of this frozen coast ; but, on the whole, there was open 

 sea in the offing." * 



North America. — In North America living glaciers 



* Whitney's Climatic Changes, pp. 315, 316. 



