18 



NATURE STUDY IN SCHOOLS. 



WINTER GEOLOGY. 



By Wm. D. McPherson. 



Winter geology is glacial geology. How could it well be other' 

 wise? In spite of the cold, we can still observe the rounded outlines 

 of the New England hills, as we spin along, in a sleigh, or take a 

 brisk walk. Many hills were formed in the long glacial winter, and 

 all were modified in form. How appropriate to study them at this 

 season. There were doubtless always hills and valleys, from the time 

 the first island appeared above the ocean, but the first hills were dif- 

 ferent than ours now. Most of the original rocky crust of the earth lies far 

 below under our feet, and the hills we see daily are composed of a 

 superficial deposit of sand, gravel, clay or boulders which have been 



Figure 16. 



A, moraine: B, kame, 



piled up on the rocky crust of the earth by glacial action. The val- 

 leys and hollows have likewise been scooped out by the tremendous 

 flowing action of huge masses of ice during the glacial age, which 

 was ten thousand years ago, or longer, 



A few hills in New England, called "out-crops", are composed 

 of a part of the rocky crust, which protrudes up through the usual 

 earth covering of sand or gravel. Prospect hill in Waltham is an 

 example. 



The great glacial ice cap that covered the Northern half of the 

 United States, reached from the North Pole to a point covered by the 

 city of Cincinnatti. Finally ,as the weather became warmer, and the 

 ice cap began to melt away, immense rivers of water were let loose. 



