IN THE DEGRADATION OF THE LITHOSPHERE. 379 



base level produced by erosion was followed by a rise of land 

 masses and a return of the cycle of erosion, and so on to an in- 

 definite extent. From what has just been stated previously it will 

 be seen that I conceive these fundamental earth joints to have 

 played an active, possibly a controlling, part in paleographic his- 

 tory. The connection and disconnection of land masses, the open- 

 ing and closing of channels of sea migration, the filling up of chan- 

 nels by the rapid formation of beach gravels and tide flow ; the 

 formation of tide and sand flats and bowlder and pebble flats (Fig. 

 4. Plate VII) such as are so common along the upper Atlantic 

 coast line (glacial in many cases, no doubt, but still due to jointing), 

 must all have played their parts in past geographic changes of both 

 .land and sea. The jointing which may doubtless be observed in the 

 Alaskan coast in the neighborhood of Behring Sea, would, under 

 these circumstances, be an active factor in the separation of land 

 connection between America and Europe, and Asia. 



Furthermore, according to this hypothesis of joint control, the 

 destruction of a great continental mass of land across the northern 

 hemisphere, which seems to be indicated by the fact of the relics 

 of such a mass in the islands of the north of Europe and North 

 America, and the distribution of islands in the Arctic Sea, all with 

 their connected deposits of Paleozoic and Mesozoic, becomes a pos- 

 sibility explainable upon more definite grounds than simply the 

 hypothesis either of sea aggressions alone or of glacial or other 

 erosive processes alone. This continental destruction is indicated 

 by the character of the sea clifi:'s of Spitzbergen and their rapid 

 angular disintegration and the reduction of the lithosphere through 

 a series of blocked islands which are now disintegrating under the 

 structural weakness of joints and the transporting power of marine 

 erosion. The details of this may be seen by reference to the lit- 

 erature. Thus the islands of Franz Josephs Land, Spitzbergen, and 

 Bear Island in the Arctic Sea ha\e been appealed to by various 

 authors in illustration of the theory of jointing. I. D. Scott^^ and 

 Hobbs-* reproduce the figure from the original exploring expedi- 



-3 Op. cit., pi. 2. 



24 Hobbs, Bull Gcol. Soc. Amcr., Vol. 22, pi. 8, Fig. 2. 



