Notices respecting New Books. 497 



crystals irregularly distributed. The relative positions of any two 

 interpenetrating crystals may be very variable, but in some cases 

 the grouping of the crystals is found to obey a definite law. It 

 is this second class of crystal groupings that is studied by the 

 author of the little book before us. After an introductory chapter 

 on crystalline structure in general, and another which is devoted 

 to a brief historical survey of the subject-matter in hand, the 

 author considers the laws which govern the formation of regular 

 crystal groupings. The remainder of the book is devoted to a 

 classification and detailed examination, with illustration*, of the 

 various forms of groupings, the last chapter dealing with the 

 transformations which crystals may be made to undergo when 

 subjected to mechanical stress. The book forms a A'aluable con- 

 tribution to a difficult and intricate problem. 



Becherckes Experimentales sur Us Oscillations Electriques. Par A. 

 Turpain. Paris : Librairie Scientifique A. Hermann. Pp. 1-154 

 1899. 

 The title of this book precisely describes its scope. It is an 

 account of the author's important and careful researches on electro- 

 magnetic waves ; many of the results contained in it have already 

 appeared elsewhere, but all interested in the subject will be glad 

 to have so complete and systematic an account of the author's work 

 in book-form. 



Perhaps the most striking feature of the book is the rigid, 

 almost austere, exclusion of everything m the shape of mathematics. 

 All controversial theoretical matter is carefully avoided, and 

 the author abstains from the use of mathematical symbols in a way 

 which cannot but be impressive to those who, to use the phrase of a 

 well-known physicist, are accustomed to regard electrical pheno- 

 mena through a cloud of analytical symbols. 



The cautious accuracy of the author's exposition reminds one of 

 the style of Faraday's Experimental Researches. The book is one 

 which may be read with interest and profit by the beginner in the 

 subject, and it will prove of still deeper interest to the advanced 

 student. 



In the first chapter, the author gives a detailed description of 

 the vibrators and resonators used by him, and the methods of 

 concentrating the Hertzian field between two wires or sheets of 

 metal. Chapter II. deals with the methods of measurement. 

 Chapter III. contains an experimental analysis of the field, the 

 properties of the field concentrated by a couple of wires being 

 deduced from those of a field concentrated by a single wire. 

 Chapter IV. deals with the action of the resonator. In Chapter V. 

 we have a most instructive account of the effects produced by using 

 oil and water as dielectrics. Chapter VI. is a useful resume of the 

 principal experimental results established by the author; and 

 Chapter VII., which concludes the book, is devoted to a peculiar 

 system of non- wireless Hertzian wave multiplex telegraphy devised 

 by the author. 



Phil. Mag. S. 5. Vol. 49. No. 300. May 1900. 2 M 



I 



