i8o HUTTONIAN THEORY 



operations. Knowing that during the passage of an 

 earthquake a territory bordering the sea may be 

 upraised or sunk, a few feet, they drew the sweeping 

 inference that any amount of upheaval or depression 

 of any part of the earth's surface might be claimed 

 in explanation of geological problems. The progress 

 of inquiry, started here by Agassiz, while it has some- 

 what curtailed this geographical license, has now made 

 known in great detail the strange story of the Ice- Age. 

 There cannot be any doubt that after man had 

 become a denizen of the earth, a great physical change 

 came over the northern hemisphere. The climate, 

 which had previously been so mild that evergreen trees 

 flourished within ten or twelve degrees of the north 

 pole, now became so severe that vast sheets of snow 

 and ice covered the north of Europe and crept 

 southward beyond the south coast of Ireland, 

 almost as far as the southern shores of England, and 

 across the Baltic into France and Germany. This 

 Arctic transformation was not an episode that lasted 

 merely a few seasons, and left the land to resume 

 thereafter its ancient aspect. With various successive 

 fluctuations it must have endured for many thousands 

 of years. When it began to disappear it probably 

 faded away as slowly and imperceptibly as it had 

 advanced, and when it finally vanished it left Europe 

 and North America profoundly changed in the 

 character alike of their scenery and of their inhabi- 

 tants. The rugged, rocky contours of earlier times 

 were ground smooth and polished by the march of the 

 ice across them, while the lower grounds were buried 

 under wide and thick sheets of clay, gravel, and 



