1895,] Mineralogy. 467 
Hecht. Introduction to the Calculation of Crystals.‘—The 
author of this valuable little book states in his preface that it gives by 
the method which originated with him, the general solution to tbe 
problems which arise in the calculation of crystals, and outlines a 
course which must, in every case, lead to the result. The necessary 
mathematical formule recommended are not difficult. A simple 
method is also given for making the stereographic and parallel projec- 
tions. Numerous examples for practice are included in the book. 
Behrens. Manual of Microchemical Analysis.’—This most 
valuable handbook is the best that has appeared treating the subject of 
microchemical analysis. Its appearance first in English, for it will 
undoubtedly be translated into German, is especially fortunate for 
American students. The book was written in English by Professor 
Behrens and edited by Professor Judd. The introductory chapter by 
the latter is an excellent resumé of the mechanical and chemical 
methods of modern petrography. Besides devising many new methods, 
Behrens has rigorously tested all the older ones, and furnishes data in 
this handbook showing the reliability and delicacy of each method. He 
has been careful to insure that errors arising from the differences in 
conditions of crystallization shall be excluded. As is well-known, the 
principle of Behrens’ method is to get the element to be determined in 
the form of a sulphate, the basis for the reactions. He insists that 
micro-chemical reactions, to come into general use, must be suited to 
work with a minimum of material and secure results in a minimum of 
time. Part I of the work describes apparatus and reagents and the 
reactions which determine each element. Part II gives a systematic 
scheme of analysis, and has special sections for the examination of 
water, ores, rocks, alloys, and combinations of the rare elements. The 
book is full of ingenious suggestion, and should be in the library of 
every petrographer. 
Baumhauer. Results of Methods of Etching in Crystal- 
lographical Investigation.’—Baumhauer, who, more than anyone 
t Anleitung zur Krystallberechnung von Dr. Benno Hecht. Pp. 76, with 1 pl. 
and 5 oiled paper charts to be used in stereographic projection. Barth, Leipzig, 
1893 
> A Manual of Microchemical Analysis, by Professor H. Behrens, with an intro- 
ductory chapter by Professor John W. Judd. Pp. xxv and 246 and 84 cuts. 
MacMillan & Co., London and New York, 1894. Price, $1.50. 
ê Die Resultate der Aetzmethode in der Lirvilaitlcgrsiihtachien Forschung, an 
einer Reihe von krystallisirten Kérpen dargestellt von Dr. H. Baumhauer. Pp. 
131, 21 cuts, and an atlas of 12 plates. Wilhelm Engelmann, Leipzig, ‘1894. 
Price, M. 16. 
