128 Heviews — Penfield's New Brushes Mineralogy. 



II. — Manual of Determinative Mineralogy, with an Introduc- 

 tion ON Blowpipe Analysis. By George J. Brush. Revised 

 and enlarged, with entirely new tables for the identification of 

 minerals, by Sabiuel L. Penfield. 15th edition. Large 8vo ; 

 pp. X, 254, 58 tables, 375 figures. (New York and London, 1898.) 



THE publication in 1896, under the editorship of Professor 

 Penfield, of a sem?-revised version of Brush's well-known 

 work on the chemical determination of minerals seemed at the 

 time a matter of doubtful policy, for would-be purchasers might 

 well have felt inclined to wait for the next edition, containing, 

 according to the editor's promise, a complete revision of the tables 

 for the identification of minerals and an additional chapter on 

 crystallograph}'^ and the physical properties of minei'als. As it 

 appears, they would not have been compelled to wait long. In 

 the present work Professor Penfield has fully redeemed his promise, 

 and has very successfully completed the work of revision which he 

 had undertaken. 



The introductory chapters remain practically the same as in the 

 edition of 1896. The most important changes, it will be re- 

 membered, were made in the chapter on the chemical reactions 

 of the elements. This was extended from the fourteen pages of the 

 older editions to ninety-four, and in its new form was eminently 

 suffg-estive and instructive. The treatment was not confined to the 

 blowpipe characters, but tests in the wet way were also given, 

 especially in the case of elements such as those of the rare earths, 

 which cannot be satisfactorily identified by the blowpipe alone. 

 The minute details given in the chapter as to manipulation and the 

 precautions necessaiy to ensure success should be of great service to 

 the student in preventing him from drawing false conclusions from 

 his experiments. 



The additional chapter in the present edition on the physical 

 properties of minerals is mainly occupied with the elementary 

 principles of crystallography. The various types of crystals are 

 grouped under the now accepted thirty-two classes according to 

 the degree of symmetry they exhibit. The Millerian system of 

 notation for the faces is explained, but no attempt is made to 

 demonstrate the mathematical relations connecting the indices with 

 the interfacial angles, etc. The object, in fact, has been to present 

 the subject in as simple (and yet an adequate) a way as possible, so 

 that the student, with the help of models, may become familiar with 

 the more important forms presented by well-known minerals, and 

 may thus be assisted in their identification. 



The subject of mineralogy comprises so many branches of 

 chemistry and physics that the author of a text-book, through 

 want of space, has generally to sacrifice one part of his subject 

 for the sake of fuller ti'eatment of others. In the present work 

 Professor Penfield gives us a very useful and instructive chapter 

 on crystallography, but from limited space draws the line at the 

 optical properties of minerals. For a description of these we are 

 referred to his colleague, Professor E. S. Dana's "Text-book of 



