332 RECENT CHANGES OF LEVEL 



southwest direction, opposing the trend of the ice current which came from the north by 

 west in a very dii*ect fashion. It will be seen, however, that the tendency has been to 

 deflect the lower part of the ice stream to the southwest, a part, however, passing around 

 to the east of the chain of hills, and a part pouring through the deep valleys of Somes' 

 Sound and Great Pond. The result of this deflecting action has been to deepen the chan- 

 nel on the west of Mount Desert nntil it is by far the most profound of all the iiords on 

 the coast of Maine. By the less considerable ice stream wdiich was turned into F'renchman 

 Bay, that great though relatively shallower excavation was formed. 



Wherever the ice moving over a plane surface is arrested b}^ any such partially sur- 

 mountable obstacle as the hills of Mount Desert, the result of the effort to mount the 

 barrier is an increase of wear at the l^ase, at the point where the change of direction is 

 brought about. To this action we doubtless owe the fact that all the elevated points along 

 this coast are separated from the main land by strips of deep Avater. It may also be noticed 

 on the main land that mountain masses, which have interposed as barriers to the movement 

 of the ice, have had the region to the north of their bases much more cut away than the 

 southern segment. Many of these barriers have extensive lakes to the immediate north. 

 This is conspicuously the case in Wachusett, Mass., and is seen in many other jjoints in 

 New England. Even in those cases where the map shows no lake basin, it will often be 

 found that extensive swamp areas mark the position of lake basins which have been filled 

 up since the glacial period. By this filling wp more than two-thirds of the area of lake 

 surface existing in southern New England at the close of the glacial period has been 

 destroyed. 



The peninsula of Nova Scotia probably turned the ice current which came down the 

 St. Lawrence, so that it sent a good part of its stream over the low col at the head of the 

 Bay of Fundy. This stream would have tended greatly to increase the excavation of that 

 singular arm of the sea, and may perhaps, in part at least, account for the prodigious depth 

 of the central abyss recently discovered there by the explorers of the United States Coast 

 Survey. 



This is hardly the place in which to undertake any inquiry into the physical histor}- of 

 the Gulf of St. Lawrence. We may, however, call attention to the fact that this great 

 basin is in all essential aspects comparable to the Great Lakes which lie at the upper part of 

 tlie valley, and must be explained in the same manner. Being at once at the end of a 

 great river system and on the sea board, it must have been swept b^^ a far stronger ice 

 stream than the upper and more interior basins. If, as it seems most reasonable to believe, 

 the great lakes, from Superior to Ontario, have been dug out by ice action, then we must 

 regard the Gulf of St. Lawrence as the product of the same forces, more gigantic in pro- 

 portion to the greater mass of the wearing agent. 



While we find ourselves forced to attribute so much Avork to the action of ice upon this 

 part of our shore, it must necessaril}- be asked how far the erosion and transportation has 

 been accomplished by the ice-time which has just passed away. All the indications of 

 glacial action being essentially superficial, its marks are in a peculiar degree liable to the 

 destruction which in a greater or less degree awaits all geological records. We have seen 

 how the secondarA' period of the last glacial time, though it brought but a thin sheet of 

 ice over the shore on the eastern coast of Maine, still SAvept aAvay from that section all the 

 great evidences of previous ice work Avhich, in the more southern district of Massachusetts 



