1889.] THE DISPLACEMENT OF BEACH-LINES. 33 



Whatever the cause origiually may have been, that lias 

 decided the division of land and sea upon our Globe, it is, it 

 appears to me, reasonable to suppose, that the movement of the 

 sea is a conservative force, that probably has contributed to the 

 continents and the oceans having, upon the whole, retained their 

 great divisions from the oldest times up to now. 



There is, thus, reason to believe that the dry lands yield 

 with greater facility than the seabottom, and that they easier, 

 than it, may rise and fall. And they are also divided from the 

 ocean depths by lines rich in volcanoes, where the connection 

 between the portions of the crust appear to be weaker than 

 elsewhere. The folding process, it may well be, perhaps, is 

 even a consequence of the movements of the tables on each 

 side not being alike. 



But the margin between the ocean depths and the base of 

 the continents does not always coincide with the present coa?t- 

 line. Along the coast there are often shallow stretches in the 

 ocean. These are the bases of continents, covered by the seas; 

 and first at a certain distance from the coast do the great ocean 

 depths appear. 



The Trias period has been so named, because it shows a 

 distinct triple division. It begins with fresh-water and littoral 

 formations; above these come formations from the deeper seas, 

 and these, again, are superimposed by fresh-water and littoral 

 formations. When it first commenced, the continents lay high 

 in relation to the sea; as it proceeded the sea rose higher and 

 higher, then the land began again to rise, and when the period 

 closed, the land again lay high in relation to the sea. And 

 these great changes in the position of the beach-line were com- 

 pleted, indubitably, in the course of many lesser oscillations. 



But in the same manner as in the Trias, do similar rela- 

 tions exist, also", in other geological formations. They begin with 



Vid.-Seisk. Forh. 1889. No. 1. 3 



