342 THE ICE AGE IN NORTH AMERICA. 



with the contracted glaciers of the Alps are scarcely prepared 

 to appreciate the extent to which currents of water flow over 

 the larger glacial masses and rearrange and transport the su- 

 perficial material collected upon them. The " subglacial " 

 streams also are not always strictly subglacial, since they 

 often flow through tunnels which are midway between the 

 top and the bottom of the ice-mass. In the Muir Glacier, 

 Alaska, for example, the two streams issuing from the ice- 

 front near the sides of the glacier are several hundred feet 

 above the level at which the two streams emerge near the 

 center of the channel. There, also, streams of water of more 

 or less size can occasionally be seen pouring out from the 

 perpendicular front of the ice a hundred or more feet above 

 the surface of the inlet. Nor is it any uncommon thing to 

 see icebergs move off with water -worn tunnels in them 

 which are still well filled with gravel and pebbles. In the 

 various depressions in the surface of the glacier also, where 

 at times extensive lakes of water are formed, there is much 

 accumulation and assortment of earthy material far back from 

 the terminal margin of the glacier. 



We will now endeavor briefly to reproduce the conditions 

 in New England near the close of the Ice age, in order to 

 see how the facts fit into the theory just enunciated. 



The main north- and-south valleys of New England are 

 now drained by the St. John, the St. Croix, the Penobscot, the 

 Kennebec, the Androscoggin, the Merrimack, and the Con- 

 necticut Rivers, with various smaller subordinate drainage- 

 basins, such as the Machias, the Saco, and the Piscataqua. 

 The larger valleys are also joined by various subordinate 

 ones, tributary to them, running in various directions con- 

 formable to the general contour of the country. But the 

 present course of the rivers is not necessarily determined 

 at every point by barriers of any great height. For exam- 

 ple, there are no high barriers separating the northeastern 

 portion of the Penobscot drainage-basin from the sources of 

 the St. Croix and Machias Rivers. South of the Rangeley 

 Lakes, also, where Ellis River joins the Androscoggin, it is 



