WINTER GEOLOGY. 



19 



These sculptured out channels for themselves, many of which remain 

 to this day. Our own Charles River, flowing into Boston Harbor, 

 was one of these sub-glacial streams. At first it flowed under the 

 ice, and afterwards when its channel was made, it still continued to 

 drain the land. 



The Mississippi was then ten times the size it is now. In going 

 over the granite hills of New Hampshire, the ice sheet broke off frag- 

 ments of rock of all sizes and rolled them along to the south, crumb- 

 ling and crushing them often smoothing them into rounded pebbles. 

 These pebbles, stones and boulders, with the sand and clay that was 

 rolled and washed along with them, now form what we call gravel 

 beds or pits, and every town has many of these gravel deposits, 

 formed from material brought from the north. 



The different markings and material left after the glacial period have 

 received various names to distinguish them. Instead of lumping the 

 material together simply as hills and valleys, we have a certain 

 kind of hill known as a kame, and another as a moraine etc. 

 Here are also kettle holes, boulders, drumlins, moulins, terraces, till, 

 etc. etc., and . for markings they have scorings, striae, grooves, etc. 



Like running water, moving ice is a powerful agent in transport- 

 ing rocks and earthy debris. This material is left on the path or at 

 the termination of the glacier. Such a line of debris is called a mo- 

 raine. When it forms along the edge of the ice, it is called a lateral 

 moraine, and at the end of the glacier, a terminal moraine. Many 

 moraines appear to have been moulded finally by the ice into what 

 are called drumlins. Drumlins are abundant in the vicinity of Boston, 

 and constitute nearly all the islands in Boston harbor, and on the 

 main land, Beacon hill, Bunker hill and many others could be cited. 

 While the glacial material piled up promiscously may be called 

 a moraine, a hill that is built up more by water action, and has 

 its material, generally sand or gravel, sorted and stratified, is known 

 as a kame. Karnes are also very abundant around Boston and 

 all over New England. If one has the leisure to follow the Charles 

 River along through Watertown, Newton, andWaltham, many instruc- 

 tive remains of glacial action will be seen along its banks, and as 

 the river was probably at least a half mile wide in the glacial period 

 the ground for this distance remains strewn with kames and other 

 debris. 



(Two good books on glacial geology are "Man and the Glacial Period" and " The 

 lee Age in North America," both by Wright, and obtainable in most all public libraries ) 



