138 T. C. CHAM BERLIN 



The exceptions, so far as there are any, probably all lie in the dis- 

 rupted border tracts on the edge of the ocean basins or the borders 

 of the continental protuberances, i.e., on the junction tracts 

 between the great elevations and depressions. 



The conclusion that continents and the ocean basins have been 

 permanent in their essentials, thus so strongly supported by strati- 

 graphical and paleontological evidence, is in complete harmony 

 with the modern geodetic argument from the distribution of gravity 

 and with the theory of isostasy, whichever of its phases be accepted. 

 It is, at the same time, consonant with the dynamical inferences 

 that spring from the deep differentiation of the specific gravities of 

 the crust. It falls in with all the views drawn from other sources 

 thus far set forth in this series of articles. Permanent ocean 

 basins, gathering abysmal sediments ever since deep oceans began, 

 alternating with permanent continents, always girt about and 

 overlain by sea-shelf deposits and foreset bordering sediments, are 

 regarded as the great fixed features of the earth's mature history. 



The view that the continents and the oceanic basins have been 

 permanent since the earth-body attained its maturity does not of 

 course go so far as to afhrm that there were no encroachments of 

 the oceans upon the continents or of the continents upon the oceans, 

 or that there were no transfers of bordering blocks or folds from the 

 one to the other. In the very nature of the case, there must have 

 been pressure contests along the borders, and the dividing lines 

 may well have shifted more or less. Growth and creep seaward 

 from the continents is assumed as probable, and periodic counter- 

 thrusts landward from the ocean basins are assumed as more than 

 probable. Advances and recessions on the border lines and 

 oscillations up and down are thus of the nature of the case. 



Though the continental segments, because of their lesser specific 

 gravities and their convex attitudes, tended, when under lateral 

 pressure, to upward movement, and the sub-oceanic segments, 

 because of their higher specific gravities and their concave forms, 

 tended, under lateral pressure, to downward movement and under- 

 thrust, reversals of these natural movements would be probable in 

 exceptional cases because of the complexity of the conditions; and 

 so continental folds or blocks might well become abysmal, and 



