122 G. II. Stone— Glacial Sediments of Maine. 



Art. XY. — Classification of the Glacial Sediments of 

 Maine; by George H. Stone. 



This paper assumes the now quite generally accepted theory 

 of Torell and Hoist as to sub- and infra-glacial matter, i. e., 

 that the till of New England consists in part of a ground 

 moraine and partly of matter that was distributed through the 

 lower portion of the ice-sheet. 



Preliminary. — It is evident that every glacier is to a con- 

 siderable extent bathed in its own waters and is drained by a 

 system of glacial streams. The escaping waters continually 

 carry away their load of detritus. The largest ice-sheet must 

 have its system of drainage as inevitably as an ordinary Alpine 

 glacier that is confined to a single drainage basin. The hypo- 

 thesis that a given region was covered with land ice must 

 carry the burden of proving that there was, over the region in 

 question, a system of glacial drainage. The presence of such 

 a system furnishes a crucial test between the theories of land 

 ice, and icebergs or other forms of floating ice. 



Reasoning from the analogies of the Alpine glaciers com- 

 pared with what is known of the Greenland ice-sheet, I infer 

 that near the front or lower extremity of every glacier (margin 

 of a body of confluent glaciers or ice-sheet), there is a belt 

 where the ice is so shattered by crevasses that the melting 

 waters almost immediately escape to the ground. This part of 

 the glacier is almost wholly drained by sub-glacial streams. 

 Back of this zone is another where the drainage is chiefly 

 effected by means of streams which flow in well defined chan- 

 nels on the surface of the ice, but at the last reach a crevasse 

 down which they fall and escape by sub-glacial tunnels. Still 

 farther back is a region which answers to the snow fields of 

 central Greenland. Here the melting waters of summer are 

 diffused through the unconsolidated snow of the preceding 

 winter and slowly seep through the soft slush, but have not a 

 motion sufficiently rapid to cause them to gather into streams 

 and erode well-defined channels. The three regions just 

 described pass one into the other by degrees. The breadth of 

 these respective belts I infer to be determined chiefly by the 

 rate of change in temperature as we go from the end of the 

 glacier backward. The slower the rate of change in tempera- 

 ture the broader will be these belts. The gentle slopes over a 

 large part of New England would tend to a slow rate of 

 change in temperature, while the fact that these slopes were 

 southward would cause a more rapid change, since it would 

 introduce the effect of latitude on temperature. On the whole 

 I estimate that these zones were pretty broad in New Eng- 



