REPORT OF THE DIRECTOR 1920-21 137 



seem to us to be that there was a continuous movement that slowly- 

 extended the folding into the continents, and that not being very- 

 intensive, may have allowed the numberless batholithic and lac- 

 colithic intrusions, but that at times broke into a more violent 

 character of worldwide orogenic paroxysms and then carried the 

 folding and extensive volcanic and intrusive activities far into the 

 interior and finally throughout the whole arch-continents. 



Whether, however, a slow continuous movement or pulsatory, 

 more violent movements of the zone of rock flowage, or both, carried 

 forward the folding into the continents from the underbodies of 

 the oceans; the fact that is important for our inquiry remains that 

 the results of these movements postulate original differences in 

 the density of the outer crust, which controlled the direction of 

 the movements and of the resulting folding, while the movements 

 themselves were only the agents furnishing the folding force. 



4 Possible cosmic agencies of Precambrian folding. 



We have, in the preceding chapters, seen how the grand uniform- 

 ity between the general Precambrian folding in North America and 

 Eurasia and the supposed coast lines of the two arch-oceans, there 

 recognizable, indicate a controlling influence of the ancient boundar- 

 ies between oceans and continents upon the forces that, emanating 

 from the underbodies of these oceans, folded the Precambrian 

 rocks throughout the continents. 



There are, however, other elements recognizable in the general 

 trends of the Precambrian folds that do not seem to be readily 

 brought into correlation with the ancient continental coast lines, 

 and that are so equally distributed within certain belts, around the 

 earth, that they suggest another factor than is furnished by the 

 Precambrian continents and oceans. 



These elements are (i) the north-south directions of the equatorial 

 belt of Precambrian folds and (2) the large east-west component 

 of the folding in higher latitudes. 



We have seen the north-south direction clearly developed in 

 Africa, Madagascar and west and south Australia; predominant 

 in East India and prevailing in folding that probably is more or 

 less posthumous in character in eastern Australia and in South 

 America. 



The east-west component appears in the northeast and northwest 

 directions of the Precambrian of the Sinian and Sayan systems in 

 Eurasia; it is emphasized by its prevailing (east-northeast direction) 



