162 SCIENCE PROGRESS 



but it is most unsatisfactory from the point of view of the Physics student, and 

 some direct hint as to the derivation of the solution is always desirable. 



After an introduction dealing with a few of the more important mathematical 

 theorems, e.g., Gauss' transformation, seven chapters are given up to the older 

 and fundamental parts of the subject. It is suggested that Whetham's Theory of 

 Experimental Physics or a similar treatise would serve as a useful preparation for 

 the more advanced treatment given here. A course of reading made up of these 

 two books would, however, be far from complete, since necessities of space have 

 constrained the author to leave all side issues {e.g. the method of electric images) 

 severely alone. A book, such as Foster and Porter, dealing with these portions 

 of the subject more thoroughly would be necessary to cover the ground adequately. 

 All through special attention has been paid to methods and apparatus used in 

 ionisation work, and in this connection it is surprising to find only the old incom- 

 plete theory of the quadrant electrometer, although Dolezalek's latest "Binant" 

 pattern is referred to. The chapter on electric currents is rather more elementary 

 than any of the others. It contains an account of Eichenwald's experiments on 

 the magnetic effect of a moving charge, a subject which generally suffers from a 

 most undeserved neglect ; but in the section on the variation of resistance with 

 temperature there is no reference to Kamerlingh Onnes' latest experiments. 

 Electrical instruments of all kinds are described and illustrated including the newer 

 types of galvanometers, viz., the string galvanometer, the vibration galvanometer, 

 and DuddelFs thermo-galvanometer. 



Chapters X-XIV (270 pages) are concerned with the modern branches of 

 electricity and are intended as introductions to the special treatise. The subjects 

 dealt with are Electrolysis, Electric Oscillations, Conduction through Gases, 

 Radioactivity and the Electron Theory. They are uniformly excellent throughout 

 and only a brief mention of some of their contents is possible here. The chapter 

 on Electric Oscillations includes a short account of the Electromagnetic Theory of 

 Light, a description of a simple form of laboratory apparatus for experiments on 

 Hertzian waves, and a long discussion on the transmission of electric waves along 

 wires. The latest methods of making the standard measurements are given in the 

 chapter on the Conduction of Electricity through Gases, while such special subjects 

 as Photoelectricity and Crystal Structure are touched on. The Electron Theory 

 includes an account of the Lorentz-Einstein transformation and a short statement 

 on the theory of Quanta. 



Sufficient has been written to show how valuable an addition this is to the 

 literature of electricity, and the Cambridge University Press is to be congratulated 

 on its inclusion in their catalogue. The book contains an index which might well 

 be amplified in the next edition. 



D. Orson Wood. 



A Treatise on Light. By R. A. Houstoun, M.A., D.Sc. [Pp. ix + 478.] 

 (London : Longmans, Green & Co., 191 5. Price 7s. 6d. net.) 



Despite the number of good text-books on Optics which have made their appear- 

 ance in recent years, Dr. Houstoun's treatise is a welcome addition to the literature 

 of the subject. The choice of material and the concise, yet thorough, treatment 

 make it a veritable storehouse of well-supplied information for the student who 

 has been through the purely elementary parts as treated in the first-year course. 

 In few books will one meet with such an absence of "padding," and such 

 economical use of space ; yet, withal, there is no impression of mere cramming 



