REPORT OF THE DIRECTOR 1920-21 /J. 



are -thus gradually breaking down, the enlarging ocean basins are 

 the most permanent features of the earth. 



Daly has lately (1918, 1920) advanced views similar to those 

 held by Barrell, but based on different lines of investigation. He 

 also holds that the surface of the earth was in a molten or gaseous 

 state after our globe had grown full size, basing his view mainly 

 on the condition of the other planets and of the moon, which by its 

 maria and lunar pits 1 indicates such a condition in a late stage. 

 He points out that the Precambrian basement terranes are granitic 

 on the average, while the eruptives of the ocean floors are almost 

 entirely basaltic or derivatives of basalt, and he considers both as 

 primeval differentiates, the basalt being the sunken part of an 

 intermediate magma, of which the other risen part is the material 

 now constituting the granitic terranes of the Precambrian (Daly, 

 1918, p. 120). He thus assumes a density stratification that is 

 due to a fluid earth and that led to an original separation of con- 

 tinental and oceanic tracts. The dominant gneisses and granites of 

 the early Precambrian complexes, however, do not represent the 

 primitive crust but its rearranged material. 



Similar views are held by Willis (1920) as to the origin of the 

 ocean depressions from original basalt masses and the repetition of 

 epochs of melting; and their consequent persistence from early 

 geologic or Precambrian time. A tendency to gradual widening 

 is supposed to have been induced by the formation of marginal 

 shearing surfaces. 



Summarizing the views of American authors who have speculated 

 on the age and origin of the oceans and continents, it will be seen 

 that they stand in essential agreement on the primordial age and 

 essential permanency of these fundamental features of the frame- 

 work of the earth; but as to their origin they do not agree. 



This American view, as we may well call it, which emphasizes the 

 permanence of the oceans and continents is not so generally accepted 

 in Europe. This may well be traced back to the subtle mental 

 influence of the geology of the two continents ; on one side the grand, 

 simply built American continent with its broad Archean nucleus 

 in the north, vast Paleozoic expanse in the middle, and a narrow 

 margin of marine Tertiary rocks ; and on the other hand the shattered 

 and complex European continent which suggests continuous rest- 

 lessness in its geologic history. 



In Europe we can discern at least two groups of writers, a larger 



1 Arguments which, incidentally, have since been repudiated by Chamberlin 

 (1920, p. 690). 



