Any serious attempt to decipher the pre-Cambrian paleogeography of the continents, even if only in broad outline, should be commended. An elaborate effort of this kind has very recently been made2 by R. Ruedemann, whose paper is valuable mainly because of its highly suggestive features. In it he “ventures to. suggest some possible fundamentals of pre-Cambrian paleogeography.” It is not too much to say that Ruedemann has opened up a new and important field of geological inquiry.
The present purpose is to confine attention to one very important aspect of the subject, in which the writer has been interested for some years, and this in its application to North America only. This aspect of the subject is the folding and foliation of pre-Cambrian age, with special reference to their trend-lines. This is a fundamental consideration in Ruedemann’s paper, and in his. summary regarding the principal lines of pre-Cambrian folding . . .