NATURE 



557 



RECENT BOOKS ON PHYSICS. 

 A lexi-Book of Physics. By W. Watson, A.R.C.S., 



B.Sc. (London). Pp. xxii + 896. (London : Longmans, 



Green and Co., 1899.) 

 Heat for Advanced Students. By Edwin Edser, 



A.R.C.S., &c. Pp. viii + 470. (London : Macmillan 



and Co., Ltd., 1899.) 

 Text- Book of Experimental Physics. By Eugene 



Lommel. Translated from the German by G. W. Myers, 



of Urbana, Illinois. Pp. xxi + 664. (London : Kegan 



Paul, Trench, Triibner and Co., Ltd., 1899.) 

 T T is a pleasure to welcome a general text-book of physics 

 J- by one of the younger generation of physicists, who 

 has had wide experience in the modern methods of 

 teaching and investigation. Since the general recognition 

 of physics as an experimental science, these methods have 

 changed so much that, although one could not but admire 

 the skill and perseverance shown in re-editing the older 

 text-books and writing them up to date, it was obvious 

 that a great improvement could be efifected by making a 

 fresh departure. 



In the arrangement of his book, Mr.Watsonhas adhered 

 in the main to the order of exposition sanctioned by long 

 experience, and has avoided the error, into which some 

 recent writers have fallen, of attempting to revolutionise 

 the basis of physical teaching. The author's guiding 

 principle has been convenience of sequence from the 

 point of view of simplicity and clearness of explanation, 

 and he has thus succeeded in producing a work which 

 the average student may be expected to follow with little 

 or no previous acquaintance with the subject. This is a 

 thoroughly practical basis, and will commend itself to 

 students and teachers alike. As illustrations of this 

 method, we may notice the introduction of a very useful 

 chapter on wave-motion and water waves, with explana- 

 tions of interference and other phenomena, before the 

 discussion of Sound and Light. In a similar manner, the 

 composition of simple harmonic motions is taken at an 

 early stage as an illustration of periodic motion, instead 

 of being reserved for the section on Sound. A great deal 

 is gained in clearness, and saved in space, by taking diffi- 

 culties of this kind in detail in their proper place. 



Another feature of the book which will commend itself to 

 a large class of students who are compelled to study physics 

 without the aid of the higher mathematics is the elimina- 

 tion of purely mathematical difficulties. Some limitation 

 of this kind is clearly essential in a general text-book, and 

 the author appears to have exercised a nice discrimination 

 in the selection of difficulties to be omitted. By curtailing 

 the mathematics, he has also been enabled to devote more 

 space to the explanation and illustration of purely physical 

 questions, and to include many results of recent research 

 which do not involve mathematical treatment. As an 

 illustration of these points, we may quote the chapters on 

 " Change of State," and on the " lonisation Theory of 

 Electrolysis," which subjects are treated from a modern 

 standpoint. 



In selecting the illustrations for the work, it has been 

 NO. 1589. VOL 61I 



assumed that the student will hay^e access to a laboratory, 

 and will supplement his reading with a practical course 

 of experimental work. For this reason, no attempt has 

 been made to supply elaborate figures of apparatus, or 

 descriptions of details of construction and adjustment 

 which the student can acquire much more effectually by 

 laboratory practice. The illustrations are for the most part 

 of a purely diagrammatic character, and are intended 

 solely to elucidate the text, and not to take the place of 

 the actual apparatus. There is no doubt that the general 

 appearance of the book might be rendered more attractive, 

 and its interest to the general reader, as distinguished 

 from the practical student, would be increased by the 

 insertion of a number of carefully printed and executed 

 woodcuts of instruments and apparatus ; but such illus- 

 trations belong properly to descriptive and technical 

 treatises, and would be out of place in a text-book. Dia- 

 grammatic illustrations are really of much greater 

 educational value when carefully designed, as they can 

 be made to emphasise the essential points of the method 

 or experiment, and are more easily remembered and re- 

 produced than more elaborate pictures. The habitual 

 use of such illustrations also tends to develop the diagram- 

 matic faculty of thinking and workmg in diagrams, which 

 is so extremely valuable to the experimentalist in designing 

 apparatus or working out a method of research. 



We are inclined to think that the utility of the book to 

 the average student would be increased by the adoption 

 of a more distinctive setting for the statement of laws 

 and definitions, and that it would in many cases be desir- 

 able to emphasise more categorically the particular points 

 in each law which are capable of definite experimental 

 verification. The majority of students are too ready to 

 accept a formula, and to regard as time wasted any attempt 

 to prove it. They often acquire a fatal facility in dealing 

 with symbols, which may perhaps suffice for examination 

 purposes, but which does not correspond to a real under- 

 standing of the subject, and is of little educational value, 

 and readily forgotten. Another addition, which would 

 be of real value to the teacher as well as to the student, 

 would be a carefully selected list of numerical examples, 

 arranged to illustrate the various sections. It would be 

 difficult to make a suitable collection, as nearly all extant 

 text-books are lamentably deficient in this respect ; but we 

 are convinced that it would be of great use, and we may 

 hope to see something of the kind in future editions. 



In matters of detail a few errata may be noted by the 

 careful reader, but this is natural, if not excusable in the 

 first edition of a new book, and the majority have doubt- 

 less been already corrected. A purist might here and 

 there find fault with the turn of an expression, or a specialist 

 in some particular department might criticise some state- 

 ment or explanation as being incomplete or misleading ; 

 but the book as a whole is remarkable for clearness and 

 correctness of exposition, and must be -regarded as a 

 valuable and original contribution to our text-books of 

 physics. 



The object of Mr. Edser's book is to give a compre- 

 hensive account of the science of Heat, both in its 

 theoretical and experimental aspects, so far as this can be 

 done without the use of the calculus. The descriptions 

 of the experiments to be performed by the students are 



