590 PETROLOGICAL ABSTRACTS AND REVIEWS 



xxiv to xxviii, appeared. It is almost impossible in the space avail- 

 able here, to abstract a book of this character. The Table of Con- 

 tents alone covers 15 pages, and a synopsis given by the author 8 

 pages. 



After describing the area covered, the author shows the various 

 subdivisions into which the Cordilleras have been divided, and suggests 

 various additions and changes. Then follow descriptions of the stratig- 

 raphy and structure of the Clarke, MacDonald, Galton, Purcell, and 

 Selkirk mountain systems, and the Rossland, Christina, Midway, 

 Okanagan, Hozomeen, Skagit, and other ranges. In chaps, ix to x the 

 Purcell lava and associated intrusives are described. The differentia- 

 tion in the Moyie sill is ascribed to the assimilation of quartzites, and 

 the writer offers proof of this as well as of gravitative differentiation. 

 A great number of chemical analyses are presented. The descriptions 

 of the rocks are given in a manner which might well be followed by other 

 petrologists, namely that of giving the mode of the rock as well as the 

 norm. Further, it is advisable, as is here done, to indicate whether 

 the mode was determined by the Rosiwal method, or by recalculation 

 of the analysis and comparison with the thin section. Pages 677 to 791 

 are mostly theoretical, and deal with the theory of igneous rocks, classi- 

 fication of igneous bodies, mechanics of batholithic intrusion, differen- 

 tiation, classification of magmas, etc. 



The report is unusually interesting, not only in the theoretical part, 

 but also in the descriptive portions, which in most geologic reports have 

 a soporiferous effect. 



Daly, Reginald A. "Problems of the Pacific Islands," Amer. 

 Jour. Sci., XLI (1916), 153-86, pi. 1, figs. 38. 

 A plea, given at the meeting of the American Association for the 

 Advancement of Science at San Francisco last August, for the establish- 

 ment of a central bureau for the comprehensive exploration, from a 

 scientific standpoint, of the Pacific Islands. It is estimated that the 

 cost of such a project will be from $800,000 to $3,000,000, depending 

 upon the thoroughness of the work, and that it will require about ten 

 years of time for the field work, and an additional five or ten years for 

 systematizing and publishing the results. The writer presents a number 

 of the problems which should be solved. 



