October 26, 191 1] 



NATURE 



547 



ELEMENTARY PHYSICS. 



(1) An Elementary Text-book of Physics. Part i., 

 General Physics. By Dr. R. Wallace Stewart. Pp. 

 v + 414. (London: C. Griffin and Co., Ltd.. 1910.) 

 Price 45. 6d. net. 



(2) Magnetismo e Elettricita. Principi ed Appli- 

 cazioni Esposti Elementarmente da Francesco 

 Grassi. Quarta edizione. Pp. xxiii + 878. (Milano : 

 Ulrioo Hoepli, 191 1.) Price 7.50 lire. 



(3) Intermediate Physics. Prepared in accordance 

 with the new regulations of Indian Universities. 

 By Prof. P. L. Narasu. Pp. xii + 637. (Madras : 

 Srinivasa Varadachari and Co., 191 1.) 



(4) Elementary Light : Theoretical and Practical. By 

 W. H. Topham. Pp. vii + 212. (London: Edward 

 Arnold, n.d.) Price 2s. 6d. 



(5) Practical Pliysics : an Elementary Course for 

 Schools. By J. Talbot. Pp. viii+112. (London: 

 Edward Arnold, n.d.) Price 2s. 



(6) .1 College Text-book of Physics. By Prof. A. L. 

 Kimball. Pp. ix + 692. (New York: Henry Holt 

 and Co., 191 1.) Price $2.75. 



(7) Die Elektrizitat. By Prof. F. Adami. Erster 

 Teil. Pp. 127. Bucher der Naturwissenschaft, 

 herausgegeben von Prof. S. Giinther. 9. Band. 

 (Leipzig: Philipp Reclam, junr., n.d.> Price 40 

 pfennig. 



(1 ""pHIS volume is presented as part i. of the series 

 1 by the late Dr. Stewart, although the 

 volumes on sound, light, and heat have already ap- 

 peared, and publication occurs subsequently to the 

 unfortunate death of the author. It may be said at 

 once that as regards mode of treatment, type, and 

 diagrams, this part is uniform with those which 

 have preceded it, and deserves the same praise as has 

 been given to them. There are one or two points, 

 however, which call for criticism, and the first is with 

 reference to the title. Actually, the contents are chiefly 

 concerned with what is usually termed mechanics, 

 and only a comparatively small portion is devoted to 

 the ordinary physical properties of matter. Strictly 

 speaking, of course, mechanics is a section of physics, 

 and its inclusion, especially if treated experimentally 

 rather than mathematically, is desirable in every ele- 

 mentary physical text-book. It is unfortunate, how- 

 ever, when, as in this case, such inclusion has secured 

 the exclusion of several essentially physical properties 

 of matter and the inadequate treatment of many 

 others. Thus we find, for example, the viscosity of 

 liquids only briefly referred to, and no mention at all 

 of the same property in gases. The second criticism 

 is in connection with two definitions in the mechanics 

 which are vague and even misleading. In common 

 with so many other text-books on this subject, this 

 book lacks the fundamental definition of "mass." 

 The author introduces the term "mass" without 

 definition in order to define force, and then uses this 

 definition for the purpose of defining mass. Few 

 writers on mechanics appear to realise that a definition 

 of mass apart from force is the essential first step from 

 the point of view of absolute measurement. The 

 other definition to which exception may be taken is 

 that of simple harmonic motion in terms of the uni- 

 NO. 2 19 1, VOL. 87] 



form motion in a circle of a second particle. The 

 effect of this is to suggest to students that this second 

 particle really exists in all cases of simple harmonic 

 motion. 



(2) The fourth edition of this book has been pro- 

 duced in order to include the numerous and important 

 advances in this subject which have been made since 

 1902, particularly those which have practical applica- 

 tions. The subject is treated in considerable detail, 

 but essentially from a non-mathematical point of view, 

 and it should be possible for a novice to obtain con- 

 siderable insight into the fundamental principles of 

 magnetism and electricity, and the many useful de- 

 vices depending upon them. The earlier chapters are 

 devoted to the usual descriptions of phenomena and 

 statements of laws in electrostatics, magnetism, and 

 current electricity, but, owing to the absence of mathe- 

 matics, exact treatment is impossible, and the absolute 

 units of potential, current, &c, are not defined. 

 Although the obvious intention of the author is to 

 lead up to what is practically electrical engineering, 

 some space is devoted to descriptions of radio-active 

 phenomena and the electronic theory of conduction 

 through gases. The final chapters on telegraphy and 

 telephony — both wireless and otherwise — and the appli- 

 cations of electricity to traction are the most detailed 

 in the book. Good diagrams are given, but some of 

 the photographic reproductions leave much to be 

 desired. 



(3) Whatever may be said of the merits of this book 

 in other respects, there can be no two opinions con- 

 cerning its chief failings. These are the obvious 

 carelessness both in correcting the proofs and in pro- 

 ducing the very numerous diagrams. Upon opening 

 the book we are met at once by two pages of errata, 

 containing some sixty or seventy corrections to the 

 text. That these are, nevertheless, incomplete is indi- 

 cated by a rather amusing mistake on p. 30, where 

 we are told that " the direction of gravity is shown by 

 the ' plum-bline.' " It may also be mentioned that 

 the diagram illustrating this instrument is a typically 

 poor one. Many of the figures, besides being badly 

 printed, follow the old style of depicting hands, or 

 even complete persons, performing certain experi- 

 ments. The book is specially designed to meet the 

 requirements of students preparing for the inter- 

 mediate examinations of the various Indian univer- 

 sities, but the author claims that it is suitable for the 

 initial stage of any college course. For some reason 

 it is not divided into chapters, nor even into distinct 

 sections dealing with the various parts of the subject 

 — an arrangement which may tend to confuse the 

 student. With regard to the subject-matter, here 

 again we find the same vagueness in defining "mass" 

 as has been mentioned above in the criticism of Dr. 

 Stewart's book. This inexactness occurs in several 

 other places, notably in the following statement : — 



"The absolute unit of potential is too large. Hence 

 ,J 5 of the electrostatic absolute unit of potential is 

 taken as the practical unit of potential and is termed 

 a volt." 



A similar erroneous description of the " coulomb " 

 is also given. 



(4) The autlfor has prepared a book comprising the 



