134 NEW YORK STATE MUSEUM 



the Precambrian on the contrary, proved in this paper, for the 

 greater part of the earth, demand an explanation by another cause 

 than the uniform contraction of a homogeneous earth crust. There 

 appear to us two hypotheses worthy of consideration in this con- 

 nection : 



a The orderly arrangement of the Precambrian folds is mainly 

 due to the influence of preexisting differences in the earth crust. These 

 would consist, according to present knowledge of the composition of 

 the crust, of lighter and heavier segments representing the continents 

 and oceans. These differences are considered as original, as we have 

 seen before, resulting either from the mode of separation of the 

 planetesimal material that built up the earth, or the continuous 

 outpouring of heavier lavas in certain regions that became the oceanic 

 basins. We have, in this paper, attempted to demonstrate that the 

 trend lines of the Precambrian rocks do, indeed, show a control by 

 a preexisting regional differentiation of the earth crust, and that 

 the regions thus recognized and marked off, correspond to the later 

 continents. 



b The Precambrian trend lines are mainly controlled by cosmic 

 influences. As such we have cited, in the preliminary paper, the 

 tidal waves of the earth crust and changes in the velocity of rotation 

 of the earth. 



3 Control of the trend lines by the continental segments 



The first hypothesis, that of the control of the trend lines by the 

 continental segments, is supported by all the evidence we have brought 

 forward of the parallelism of the Precambrian trend lines with the 

 coast lines of later continents and the general agreement of the arch- 

 continents of Precambrian time with those of Paleozoic time. It is 

 further supported by the present views of geologists on the processes 

 of folding in general. While the older geologists currently considered 

 the folding of the earth crust as a simply superficial process due to 

 horizontal or tangential compression of the shortening earth crust from 

 the surficial cooling of the globe, the conviction has been steadily 

 gaining ground that this assumption is not able to explain the facts of 

 arrangement of the mountain systems and other problems. Suess 

 (v. 3, pt 2) from his study of the mountain ranges, especially of 

 Asia, reached the view that the stratosphere and a large part of the 

 salic crust do not fold themselves but are folded, are passive and 

 carried forward, a view which seems to be supported by the recent 

 experiments of Meade (1920, p. 52 1) who concluded that " most of the 



