Shaler.] 182 [June 16, 



alone. The evidence to my mind is irrefragable that this region had 

 its essential topographical features, all its valleys and fjords, before 

 the last ice time. Undoubtedly, in many successive periods we may 

 have had enough wearing applied to the hills to give them their form. 



Some years ago I endeavored to account for the erosion of lake-ba- 

 sins of the glacial period by the melting of the ice beneath the glacier 

 from the outflow of internal heat. This clearly is an insufficient cause 

 to explain all the action, but I still believe it to have been a true cause. 

 Taking J. D. Meyer's computation, and supposing that the waste of 

 heat from the earth's interior is two hundred cubic miles per diem, 

 one-half from volcanoes, there will be about one foot of ice melted 

 beneath the continental glacier each year; as this heat will escape 

 principally in the bottom of the valleys, it will directly cooperate 

 with the pressure melting. As long as the water remained in the 

 shape of ice, the escape of heat from below would be in a measure 

 retarded; the instant a part of this ice was melted into water the 

 escape of heat from the earth would be greatly aided, and would 

 become very rapid, and in this way the continued fluidity of ice ren- 

 dered liquid by pressure, would be secured. 



These propositions may be briefly summed up as follows: — 



1. That the melting caused by pressure would put a limit to the 

 accumulation of ice at a depth of probably not exceeding two miles; 

 probably much less. 



2. That while the ice resisted the passage of heat from the earth, 

 the water would favor this action, and so enable the water, fluid from 

 pressure, to move to regions having a considerable less pressure. 



3. Some melting would take place beneath the ice from the heat 

 of the earth alone ; this would, in itself, be sufficient to produce con- 

 siderable effects. 



4. The melting from pressure would give the ice-sheet a chance 

 to move freely in the direction of least resistance. The water would 

 not be able to rise through the unmelted ice on account of the re- 

 moval of the pressure, to which it owes its melting. 



5. The flow of water, more or less spasmodic and flood-like, to- 

 wards the border of the ice, would suffice to carry away the rain-fall 

 of the region, and to push forward pebbles to great distances ; it 

 would account for the stratification of moraine matter far above the 

 sea, and for the rounding of pebbles. 



6. The scoring of the rocks, which gives evidence of movement 

 and of the direction whence it came, are necessarily the work of the 



