IN THE DEGRADATION OF THE LITHOSPHERE. 369 



fjords are submerged valleys, that still does not explain the parallel 

 structure which is to be observed on both sides of the north Atlantic 

 coast ; indeed, the similar character of the rock structure on the 

 north Atlantic coast, in America and Europe both, and in the islands 

 of the Arctic Sea, demand a general structure rather than simply a 

 general agent. 



When the discussions of principles concerning fjord structures 

 are applied generally to a wide tract of the earth's surface, such as 

 for example the North American continent, certain points may be 

 shown, and I wish to suggest that that part of the North American 

 continent included between lines drawn from the mouth of the 

 McKenzie river through Great Bear Lake and Great Slave, Atha- 

 baska, Winnipeg, and the Great Lakes and another line drawn from 

 Cape Cod to Nova Scotia parallel in general with the St. Lawrence 

 river up to Newfoundland, is controlled by a series of master joints 

 whose general angles of direction may be read from the lines of 

 present sea-coast, lake distribution, entrance of sea channels, bays 

 and harbors and that these are all to be conceived of as essentially 

 attributable to a general cause which is independent of local condi- 

 tions and is an essential part of the structure of the North American 

 continent. Further, that this great extent of continental land has 

 been in the past and is now, although it is often regarded as one of 

 the fixed segments of the lithosphere, undergoing disintegration and 

 degradation in a manner controlled essentially by something which 

 is independent of atmospheric contact and may be explained on the 

 supposition of the falling apart of a series of segments of the earth 

 due to the development of these lines of jointing. I conceive this 

 disintegration and development of jointing to be due to the loss of 

 elasticity in this portion of the lithosphere. This mass of the conti- 

 nent has been since Archean times loaded repeatedly by the recep- 

 tion of sediments extending from early Paleozoic to Mesozoic times, 

 it has been flooded from time to time by water, overrun by glacial 

 ice, and even if not presumably subjected to elevation or subsidence 

 it has nevertheless been subjected to a series of earth pressures and 

 strains so that a series of master joints have become a primary part 

 of its structure. 



That under the combined attack of atmospheric weathering in 



