;s6 



NATUJiE 



[November 28, 191: 



g-ood view of the author's personality. With all 

 his genius, Poincare was an orthodox thinker by 

 nature; in the case of non-Euclidean geometry, 

 which he fully appreciated, his criticisms are acute 

 and valuable ; his sceptical attitude towards 

 Cantor's theory of transfinite numbers is amusing, 

 Init not altogether surprising, and is perhaps the 

 only instance of his shutting his eyes to a great 

 mathematical discovery. Kelvin's long opposition 

 to the electromagnetic theory of light is another 

 illustration of the same sort of thing. 



To give a just estimate of the value of the 

 researches of Henri Poincar^ is not possible at 

 the present time, nor is it necessary. The almost 

 immediate recognition they obtained, the increas- 

 ing impression of their fundamental importance, 

 and the numbers of students who have followed 

 and expanded the ideas which he laid down with 

 so sure a hand are the best testimony of their 

 worth. We do not know what further contribu- 

 tions he would have made to mathematical science, 

 Iiad he lived, but we do know that what he 

 achieved gives him a permanent place in the 

 history of the subject. 



THE PHYSICS OF THE UNIVERSE. 

 Lehrbuch dcr kosmischen Physik. By Prof. W. 

 Trabert. Pp. x + 652. (Leipzig and Berlin: 

 B. G. Teubner, 191 1.) 



THE primary justification of a treatise on 

 cosmical physics is to be sought in the 

 principle that economy of communication is of the 

 very essence of science. The author of such a 

 hook cannot hope to deal so competently with the 

 individual subjects as the experts to whose 

 writings he must have recourse for his own know- 

 ledge, but his work will be a real contribution to 

 the progress of science if he succeeds in imparting 

 unity to his treatment of subjects which have been 

 developed by different workers, each more or less 

 superficial in his knowledge and appreciation of 

 tlie work of those outside his own branch. Judged 

 from this point of view Prof. Trabert's book is 

 successful. It has been developed according to a 

 definite and well-ordered scheme. 



A natural impulse is to compare the book with 

 the masterly treatise with the same title which 

 .\rrhenius published ten years ago. The principal 

 difference between the two works is in size and 

 iirder. The older book covers 1000 pages, of 

 which about 400 are devoted to meteorology ; the 

 new one contains 650 pages, of which only about 

 100 can be spared for meteorology. Arrhenius 

 sl.'irts with the " Physik des Himmels," the stars, 

 the sun, the planets, and proceeds from that to the 



xo. 2248, VOL. go] 



" Physik der Erde," the form and constitution ot 

 the earth and the sea, the tides and the ocean 

 currents. He deals finally with the " Physik der 

 .Atmosphare," meteorology, atmospheric elec- 

 tricity, and terrestrial magnetism. Trabert begins 

 with an introductory chapter on the fundamental 

 ideas of the physical concept of the universe. He 

 then deals in order with the form of the earth and 

 its place in the universe, the phenomena of motion 

 — the motion of the sun, the stars and the earth, 

 and tidal and earthquake phenomena, the pro- 

 cesses of radiation, with especial reference to the 

 earth's atmosphere, the exchange and transform- 

 ation of energy, and finally with the development of 

 the universe. Position, motion, energy, result, may 

 be taken to represent briefly the order adopted. 



A feature of the book is the care with which the 

 historical development of the principal methods 

 and ideas has been treated, and the retrospective 

 chapters at the end of each section are especially 

 interesting. Thus in the first section the deter- 

 mination of the distances of the sun and moon is 

 traced from its earliest beginnings with Aristarchus 

 and Hipparchus, down to the first exact measure- 

 ments by Lacaille and Lalande, and the results of 

 Newcomb and Gill. In the second section the 

 different arguments for the rotation of the earth 

 are set forth, including the observed deflection of 

 the wind towards the right ; we may commend to 

 those who are sceptical of the effect of the earth's 

 rotation upon motion along the surface the 

 account, on p. 129, of the effect produced on the 

 Hamburg-Harburg railway prior to 1877. In the 

 account of seiches which is given in this section, 

 no mention is made of the work of Chrystal and 

 ^Vedderburn, and in dealing with star-streams no 

 reference is made to Schwarzschild's hypothesis 

 and the later developments. Such omissions, if 

 they stood alone, might be regarded as incidental 

 to the character of the book, but they indicate a 

 lack of appreciation of recent developments which 

 becomes astonishing when one finds no direct re- 

 ference to the most important development of 

 Prof. Trabert's own subject in recent years, i.e., 

 the discovery of the stratosphere and its explana- 

 tion, with the concurrent development of our 

 knowledge of atmospheric radiation and dynamical 

 meteorology. 



Apart from this blemish the book appears to be 

 excellent. The use of mathematical formulae has 

 been avoided as much as possible, but wherever a 

 mathematical demonstration affords the simplest 

 and readiest proof of a result or is necessary for 

 the strict development of the subject, the author 

 has not hesitated to use it ; frequently, however, he 

 has given the general outlines of the reasoning in 

 the text, and added the formal proof as a footnote. 



