PETROLOGICAL ABSTRACTS AND REVIEWS 281 



the Cross, Iddings, Pirsson, Washington system, the rocks are camp- 

 tonoses; the inner mass a grano-augite-camptonose, the envelope a 

 pitaxi-biaugi-camptonose. 



Further, there are described associated pegmatite and aplite veins, 

 and the mode of intrusion is discussed. 



Albert Johannsen 



Jevons, H. Stanley, Jensen, H. I., and Sussmilch, C. A. "The 



Differentiation Phenomena of the Prospect Intrusion," Jour. 



and Proc. Roy. Soc. N.S. Wales, XLVI (191 2), 11 1-38. 



In this paper the origin of the various segregation veins occurring in 



the Prospect intrusion is discussed. The authors assume that all have 



originated m situ during the cooling and consolidation of a single magma, 



which may or may not have been homogeneous when intruded. The 



paper is divided into two parts. In the first Jevons summarizes the 



various differentiation hypotheses, and in the second, the differentiation 



phenomena of the Prospect intrusion are discussed by Jensen and 



Sussmilch. 



A. J. 



Johannsen, Albert. Manual of Petrographic Methods. New 

 York: McGraw-Hill Book Co., 19 14. Pp. xxviii+649, 

 figs- 770- 



This publication fills a long-felt want of a comprehensive book in 

 English on petrographic methods. 



After a brief introduction on crystallographic principles and on stereo- 

 graphic projection it gives a full treatment of those parts of optical 

 crystallography of value in petrographic research, and the various means 

 of determining the optical constants. For each of the more important 

 properties, methods are given in historic order. Not only are the present 

 standard methods fully described, but those of historic interest are 

 either described or briefly outlined, with references to the original litera- 

 ture, so that one hoping to improve petrographic technique may be saved 

 much unnecessary labor by having placed before him the various schemes 

 that have been tried and later displaced by apparently more satisfactory 

 methods. The discussions are both geometrical and analytical. 



The properties of lenses are discussed and the various types of micro- 

 scopes and accessories are briefly described and illustrated, thus giving 

 the student an idea of the different characteristics of the designs of 

 instruments produced by the various European and American makers. 



