CHAPTER XV. 



THE THEORY OF THE PERMANENCE OF CONTINENTS 

 AND OCEANS. 



IT seems only fitting that a study of the geographical 

 changes of the past, even though it is concerned with 

 no more than a small portion of a continent, should con- 

 clude with some expression of opinion regarding the de- 

 bated question of the permanence or permutation of 

 oceans and continents. 



The theory of their permanence, that is to say, the view 

 that the position of the continents was fixed at the be- 

 ginning of geological time, and that oceans and continents 

 have ever since occupied their present relative positions, 

 was originated by Professor Dana, and has more recently 

 been independently maintained by Dr. A. R. Wallace and 

 Dr. A. G-eikie. 



The theory of their permutation or interchange was 

 that held by Sir Charles Lyell and other geologists, who 

 regarded the continents and ocean-basins as great upward 

 and downward bendings of the earth's crust, and conse- 

 quently liable to shift their positions entirely in the course 

 of ages, so that what was once an ocean-bed might become 

 a continent, and vice versa. 1 



The data on which Professor Dana bases his opinion are 

 entirely hypothetical ; it is, in fact, merely an inference 

 but a necessary and unavoidable inference from his 

 hypothesis of the manner in which the crust of the earth 



1 " Principles of Geology," eleventh edition, vol. i. p. 258. 



