REVIEWS 595 



That the temperatures were higher than those of pegmatites is admitted 

 by the writers, but the only thing certain about the temperatures of the 

 pegmatites is that some minerals in some pegmatites formed at tempera- 

 tures lower than 575 C. The dominance of pyrrhotite as compared 

 with pyrite is recognized, and this indicates a high temperature, since 

 pyrite is less stable than pyrrhotite at such temperatures. 



The paper represents an excellent piece of work and is a distinct 

 contribution to the knowledge of magmatic processes. It also serves 

 to emphasize the fact that a great deal must be known concerning the 

 minute textures of rock masses, other than that they are merely in juxta- 

 position, before positive conclusions may be reached as to the sequence 

 of crystallization. 



E. A. Stephenson 

 Chicago 



Relations of Cretaceous Formations to the Rocky Mountains in 

 Colorado and New Mexico. By Willis T. Lee. Prof. Paper, 

 U.S. Geol. Surv. No. 95-C, 1915. Pp. 27-58, pi. 1, figs. 11. 

 In this paper physiographic principles are applied to certain phases 

 of the stratigraphy of the southern Rocky Mountains. The geographic 

 conditions during the Mesozoic are discussed and a large number of 

 Cretaceous sections are considered. This study indicates that this 

 basin of Cretaceous deposition was deepest in northern Colorado and 

 southern Wyoming, and that the main mass of sediment came from 

 an ancient land farther west. The sections show, moreover, that the 

 sandstone formations near this ancient continent become thinner east- 

 ward, toward the present Rocky Mountains, and are replaced by shales. 

 The author concludes that the conformable Cretaceous formations up 

 to and including the Laramie once extended across the present site of 

 the mountains. Downward warping and deposition in this basin was 

 followed by uplift and erosion. This change is believed to mark the 

 close of the Cretaceous. The formations deposited after the uplift 

 (the post-Laramie formations) belong in the Tertiary. 



H. R. B. 



Review of the Pleistocene of Europe, Asia, and Northern Africa. 

 By Henry Fairfield Osborn. Annals N.Y. Acad. Sci., 

 XXVI, 1915, pp. 215-315, figs. 20, tables 4. 

 This paper is a revision for the German edition of chap, vi of the 

 author's The Age of Mammals. 



H. R. B. 



