NATURE 



121 



THURSDAY, DECEMBER 3. ic 



PHYSICS, OLD .l.VD AjETP. 

 Tlie New Physics and its Evolution. By Lucien 



Poincard. Pp. xvi + 344. International Scientific 



Series. (London : Kegan Paul, Trench, Triibner 



and Co., Ltd., 1907.) Price 54-. 

 TJic Evolution of Forces. Bv Dr. Gustave Le Bon. 



Edited bv F. Legge. Pp. XV + 3S8. (Same series and 



publishers, igoS). Price 55. 



MR. LEGGE is to be congratulated in bringing 

 before the English reader these two French 

 publications, which have been translated into vigor- 

 ous and idiomatic English. The value of each book 

 is enhanced by the addition of a table of contents 

 and an index, and of occasional notes by the trans- 

 lator of explanation or of recent additions to know- 

 ledge. 



The work of Lucien Poincare is a critical statement 

 of the position of physics to-day, with especial 

 reference to the influence of recent discovery on the 

 older ideas. In about three hundred pages he passes 

 in review a great variety- of subjects, including a dis- 

 cussion of the fundamental units, the principles of 

 physics, the various states of matter, electrolytic dis- 

 sociation, wireless telegraphy, electric conduction of 

 gases, kathode rays and radio-activity, while two 

 chapters are devoted to the ather and the connection 

 between asther and matter. In such a short compass 

 it is obvious that none of these subjects can be 

 treated in detail, but the author succeeds in every 

 case in giving a luminous and interesting survey 

 of the state of knowledge. Great care has evidently 

 been taken in studying the historical development of 

 ideas and in endeavouring to apportion the just credit 

 to various investigators. In this the author shows 

 himself unusually accurate and happy in his state- 

 ments. There is one notable exception to which atten- 

 tion may be directed. In the discussion of the principle 

 of the conservation of energy, two pages are devoted 

 to the contributions of Mayer, but no mention is 

 made of the classical experiments of Juule. 



The judicious attitude of the author is well illustrated 

 in his short account of the n-rays and in the history of 

 ■wireless telegraphy. He obviously feels that it be- 

 hoves him to step warily. A digression is given on 

 the duties of the writer of contemporary science 

 which bears quotation : — 



" An invention is never, in reality, to be attributed 

 to a single author. It is the result of many collabo- 

 rators who sometimes have no acquaintance with one 

 another, and is often the fruit of obscure labours. 

 Public opinion, however, wilfully simple in the face 

 of a sensational discovery, insists tliat the historian 

 should also act a% a judge; and it is the historian's 

 task to disentangle the truth in the midst of the 

 contest, and to declare infallibly to whom the acknow- 

 ledgments of mankind should be paid. He must, in 

 his capacity as skilled expert, expose piracies, detect 

 the most carefully hidden plagiarisms, and discuss 

 the delicate question of priority ; while he must not 

 be deluded by those w'ho do not fear to announce, in 

 bold accents, that they have solved problems of which 

 they find the solution imminent, and who, the dav 



XO. 2040, VOL. 71 j] 



after its final elucidation by third parties, proclaim 

 themselves its true discoverers. He must rise above 

 a partiality which deems itself excusable because it 

 proceeds from national pride ; and finally he must 

 seek with patience for what has gone before. While 

 thus retreating step by step he runs the risk of 

 losing himself in the night of time." 



Finally, after a happy if somewhat delicate treat- 

 ment of the history of the subject, he concludes with 

 the following quotation from Voltaire in the " Philo- 

 sophical Dictionary " : — 



" What ! We wish to know what was the exact 

 theology of Thot, of Zerdust, of Sanchuniathon, of 

 the first Brahmins, and we are ignorant of the in- 

 ventor of the shuttle ! The first weaver, the first 

 mason, the first smith, were no doubt great geniuses, 

 but they were disregarded. Why? Because none of 

 them invented a perfect art. The one who hollowed 

 out an oak to cross a river never made a galley ; 

 those who piled up rough stones vinth girders of wood 

 did not plan the Pyramids. Everything is made by 

 degrees and the glory belongs to no one." 



In a final chapter the author makes a few remarks 

 on the " future of physics." He is appreciative of 

 the great value of the electronic hypothesis, and 

 foresees that it will lead to further developments, but 

 is not so certain of its survival in its present form. 

 He states : — - 



" The electron has conquered physics, and many 

 adore the new idol rather blindly . . . but it is right 

 not to lose sight of the fact that an image may be 

 a well founded appearance, but mav not be capable 

 of being exactly superposed on the objective reality." 



The book is simply and pleasantly written with 

 an absence of all formulae and the avoidance of tech- 

 nical terms as far as possible. The non-expert reader 

 will find some of the chapters stiff reading, but he 

 will nevertheless find much to interest and instruct. 

 It is a scholarly production which can be confidently 

 recommended to all who are interested in the develop- 

 ment of physics. 



The work of M. Gustave Le Bon on the " Evolu- 

 tion of Forces " is of a very different type. If, in 

 reading the work of M. Poincar^, the critical faculty 

 rests in abeyance, in the work of M. Le Bon there 

 is an inclination to dispute the correctness of a state- 

 ment on nearly every page. The work is in some 

 respects a sequel to the " Evolution de la Mati^re," 

 previously published, which gave an account of the 

 author's views on the transformation of matter and 

 his experiments in support of them. The present work 

 is somewhat varied in character. The first half of 

 the book is devoted to a discussion of the principles 

 of physics, including the fundamental conceptions of 

 time, space, energy, and matter, and the principle 

 of the conservation of energy and of matter from the 

 point of view of Le Bon's theory. This theory is 

 engaging in its simplicity, but is in many respects 

 very revolutionary in character. The atoms of matter, 

 which are supposed to be enormous reservoirs of 

 energy, are slowly undergoing spontaneous trans- 

 formation into the aether. Matter represents a com- 

 paratively stable form of energy, but electricity, light, 

 heat, &c., are unstable manifestations of the same 

 energy, and are derived from the transformation of 

 the atoms of matter. The terms electricity and matter 



