496 PETROLOGICAL ABSTRACTS AND REVIEWS 



Boeke, H. E. "Die Methoden zur Untersuchung des molekular 

 Zustandes von Silikatschmelzen," Neues Jahrb. Min., GeoL, 

 u. Pal., B.B., XXXIX (1914), 64-78. 



Boeke, H. E. Grundlagen der physikalisch-chemischen Petro- 

 graphie. Gebrlider Borntraeger, Berlin, 1915. Pp. xii+428, 

 figs. 168, pis. 2. 



In view of the important bearing of recent physico-chemical research 

 upon the problems of the origin of igneous rocks, this work is most timely 

 and acceptable, and is to be recommended to all advanced students of 

 petrology. It is an invaluable summary of work already done, and 

 contains many suggestions for future work. 



The author not only presents the results of previous work but 

 describes in detail the methods and apparatus by which these results 

 were obtained. The subject is presented in a very clear and orderly 

 manner, and as simply as is compatible with the nature of the subject. 

 In his treatment the author follows the inductive or synthetic method, 

 that is, he describes first the behavior of the simplest constituents of 

 rocks under known conditions of composition, temperature, pressure, 

 time, etc., and compares the results with those found in nature. Begin- 

 ning with the magma, he traces it through all stages of cooling and 

 through the gradual changes which take place in its solidification products. 



In older petrologic textbooks there is a great variety of views as to 

 observed phenomena, primarily because so many factors must be taken 

 into consideration, and one or another may predominate. Since in 

 many cases there are more unknown than known factors, a single solu- 

 tion may be impossible. The synthetic method seeks to determine, by 

 exact and systematic investigation, the action of each factor, such as 

 temperature, pressure, capillarity, etc. 



In most provinces of petrology only the beginning of inductive 

 research has been made, and the experimental work so far is no more 

 than a groping after the truth. Little can be said at the present time 

 as to the formation of rocks from their complicated magmas, and physi- 

 cal chemistry can not yet settle such questions as the origin of mag- 

 matic differentiation, the relation between the alkali and alkali-lime 

 rocks, and that of dike satellites to parent rock, etc., on account of the 

 lack of reliable data. 



The present text is so comprehensive that only the very briefest 

 outline of the contents of the various chapters can be given; a list of the 



