142 NEW YORK STATE MUSEUM 



reconstruct the embryonic framework of the earth, or that which 

 was developed during the growing stage of the earth from the 

 dominant influence of the changing rotation, and which concededly 

 (see Chamberlin, 191 6, p. 203, 204) was greatly obscured by 

 secondary factors, such as dominant directions of wind and current 

 movements and " the diastrophism that sprang from secular loading 

 and unloading, and from "the shrinkage of the earth-body which 

 appears to have assumed the leadership in shaping the earth after 

 growth ceased." It is precisely this last agency which produced the 

 Precambrian compression phenomena upon which we have based 

 our reconstruction of the Precambrian continents. We may 

 therefore assume that theoretically the segmentation set forth by 

 Chamberlin took place in the embryonic, growing stage of the earth, 

 through the dominancy of the rotation factors, laying the skeleton 

 work of its frame; that this, if not entirely obliterated by a molten 

 or intensely volcanic stage, was at least obscured to a great extent 

 when after full growth was attained, the shrinking of the earth and 

 the resulting diastrophism put a different pattern on the surface 

 of the earth, namely, that which we have traced and which explains 

 the shape and arrangement of the Paleozoic and Precambrian con- 

 tinents. As Suess has repeatedly emphasized, several patterns 

 of mountain ranges have been placed in the framework of the earth 

 upon each other through successive changes in the direction of 

 diastrophic movements. It is thus explainable that the present 

 pattern of mountain ranges and even of continental arrangement 

 is quite different from that of Paleozoic and Precambrian times. 



It is logical to infer from these facts that the differentiation 

 into continental and suboceanic matter conceived by Chamberlin 

 to have taken place during the slow growth of the earth, as 

 well as the segmentation along yield tracts — both of which characters 

 by the very nature of their origin, must be deeply implanted into 

 the structure of the earth, theoretically reaching to the center — 

 should in spite of the various vicissitudes and obscuring later 

 influences of the surface, persist in the framework and be able to 

 reappear again in the face of the earth, and may therefore be now 

 again recognizable in the form described by Chamberlin. 1 



1 It certainly is very suggestive that the three great Precambrian nuclei of the 

 northern hemisphere, the Canadian, Baltic and Siberian (Angara) shields, are 

 120 of longitude apart, a fact pointed out by Dacque (1919, p. 97) ; and that these 

 ancient shields are girdled in the east, west and south by old, now strongly denuded 

 mountain ranges, which in their turn are surrounded on the outside by festoons 

 of younger chains of Tertiary age. A similar strange homology is observable 

 in the structure of the southern hemisphere, as fully set forth by Dacque. The 

 Baltic and Siberian shields are, however, not considered as belonging to different 

 continental blocks that are separated by oceanic basins in Chamberlin's scheme, 

 nor does the Precambrian folding described in this paper place them into different 

 units. 



