REVIEWS 507 



The instructions for centreing the light and illuminating appliances follow- 

 along orthodox lines, and the question of tube-length adjustment is ade- 

 quately dealt with, the methods being those described by other workers. 

 The examination of stained preparations by a dark-ground method is de- 

 scribed and recommended, but the errors of interpretation that can arise 

 under such circumstances are apparently not realised. 



The book has undoubtedly been compiled with the object of providing a 

 guide for the uninitiated, and in many respects it will fulfil its purpose ; but 

 it suffers considerably from the constant recurrence of quotations from the 

 writings of others and consequent lack of cohesion. 



J. E. B. 



Optical Theories. By D. N. Mallik, B.A., Sc.D. Second Edition. (Pp. 

 ii -\- 202). (Cambridge : at the University Press. 1921. Price i6s. net.) 



The fact that this book has reached a second edition in a comparatively 

 short time is in itself sufficient evidence of its value. The treatment of the 

 subject follows the same lines as in the earlier edition, with the important 

 addition of a brief but lucid account of the theory of relativity and the 

 quantum theory. The opening paragraph in the book indicates its scope 

 and is as follows : 



" A complete theory of optics has to furnish an adequate account, not 

 merely of the nature of light, but also of the mode and mechanism of its 

 propagation, as well as the nature of the medium in which the propagation 

 takes place. And we shall see, as we pass in review, in historical order, the 

 various theories that have been proposed, that our knowledge on these 

 points is after all extremely limited." 



The historical side is well treated, and conrists not merely of a few isolated 

 theories, but shows how these have been led up to on the basis of earlier work. 

 The chapters on the Electro-magnetic Theory and the Electron Theory are 

 especially interesting, the weak points in each case being clearly indicated. 

 The book may be commended to those desirous of obtaining a clear conception 

 of the relative value of the theories of light propagation at present available. 



J. E. B. 



First Course in General Science. By F. D. Barber, M. S. Fuller, J. L. 

 Pricer, and H. W. Adams. [Pp. vii + 608.] (New York : Henry 

 Holt & Co. ; London : G. Bell & Sons. Price gs. net.) 



" This book is written in the belief that science instruction in the first 

 high-school year should not aim primarily to survey the entire field of nature 

 and present scattered bits and choice morsels from every special science in 

 order that the pupil may decide which of the special sciences he likes best 

 and which he will omit. Nor should first-year general science be regarded 

 primarily as an introduction to, or a foundation for, the special science he 

 may later study. While it should, in a large measure, accomplish both these 

 results, it has a vastly more important function to perform. The primary 

 FUNCTION of first-year general science is to give, as far as possible, a rational, 

 orderly, scientific understanding of the pupil's environment to the end that 

 he may, to some extent, correctly interpret that environment and be master 

 of it. It must be justified by its own intrinsic value as a training for 

 life's work." 



The foregoing paragraph from the preface indicates the aim of the work. 

 In most English schools the introduction to science is a course planned to 

 lead up to more advanced work and is, in most cases, quite satisfactory for 



