IN THE DEGRADATION OF THE LITHOSPHERE. 871 



tion of this land mass becomes one of considerable interest in the 

 physical history of the area in discussion. That the usual processes 

 of land surface erosion and continental degradation are not enough 

 to explain such continental destruction may possibly be a matter of 

 opinion, rather than absolute proof. However the coal beds and 

 flora of the Pennsylvanian found in Spitzbergen, the occurrence of 

 Mesozoic deposits across practically the area of the northern part 

 of the hemisphere, the similarity of certain vital groups on separated 

 areas of this vast tract of the earth argue for the existence of such 

 a destroyed land mass, a land mass which has left its relics in the 

 form of islands in the arctic sea, in the form of indentations and 

 multitudes of channels and in the similarities which are to be ob- 

 served in the structures of the Canadian and Baltic provinces. 



The literature concerning some of these arctic islands is referred 

 to elsewhere in this paper but from their present situation and 

 methods of destruction I believe the explanation of the destruction 

 of this former land mass lies essentially in two things, a definite 

 structure in the lithosphere itself and in marine denudation or 

 degradation ; thus showing in the combination of these two elements 

 the fact of land or lithosphere surface degradation below sea level. 

 It is of course true that other forces such as change of sea level 

 may be involved in this. Since the descriptions given of the marine 

 degradation now in progress at Spitzbergen indicate a very definite 

 joint control both in the lines of fracture and in the vertical faced 

 cliffs caused by marine erosion acting against a jointed structure of 

 the rock, we may explain this along precisely the same lines that the 

 disintegration along the coast of New England and in the islands of 

 Casco Bay may be explained, that is, by jointing and the disintegrat- 

 ing eft'ect of marine and atmospheric attack. The theory that the 

 Canadian Shield^^ is a peneplain and has been so since Pre-Cambrian 

 time, is not interfered with by this suggestion ; it is rather all of it 

 involved in an attempt to explain this and other great continental 

 degradation upon more definite ground than the usual processes of 

 atmospheric agents acting as the forces of erosion. I believe it is 

 possible to show that below the zone of ordinary base leveling or 

 peneplanation lies a still further zone of possible degradation through 



18 Pirsson and Schuchert, " Textbook of Geol.," pp. 556 flf. 



