July 7, 1921] 



NATURE 



583 



judged from its latest successor, the work was 

 done neither better nor worse than usual. That 

 the original author's effort has proved more en- 

 during than Bismarck's may be accounted for by 

 its privileged sale in a particular institution. 



Had the book been confined to the permanent 

 geometrical elements, and, after the introduction of 

 more modern numerical data and the excision of all 

 archaic matter, offered for sale at one-third of the 

 price, it might have been worthy of attention. 

 The new editor claims to "have endeavored to 

 bring it up to date." The following quotation, 

 giving the latest information on radial velocities, 

 will afford a measure of the reviser's success : — 

 " Mr. Huggins, using a spectroscope of large 

 dispersive power, and carefully comparing the 

 spectrum of Sirius with that of hydrogen, found 

 that the line F in the spectrum of Sirius was dis- 

 placed, by about i /250th of an inch." 



This from America in 1920 ! To a very fair 

 account of the disappearance of Saturn's rings is 

 appended the remark : " The last disappearance 

 took place in 1907 ; the next will take place in 

 1922." Perhaps, on the whole, it is well that the 

 price of the volume should be prohibitive. 



Radio aktivitdt und die neueste Entwicklung der 

 Lehre von den chemischen Elementen. By 

 Prof. K. Fajans. Dritte Auflage. (Sammlung 

 Vieweg : Tagesfragen aus den Gebieten der 

 Naturwissenschaften und der Technik. Heft 45.) 

 Pp. viii-t-124. (Braunschweig: Friedr. Vieweg 

 und Sohn, 1921.) 6.50 marks. 

 In this book Prof. Fajans gives a simple and 

 <:lear account of the advances in chemical theory 

 which have resulted from the study of radio-activ- 

 ity. A brief description of the radio-active bodies 

 ;and their transformations is followed by an account 

 of their chemical properties, leading to their classi- 

 'fication in the periodic system, and the recognition 

 •of the existence of elements which, though dif- 

 fering in atomic weight, are identical in chemical 

 'behaviour. The author shows how Moseley 

 ^arrived at a number which is a more fundamental 

 •characteristic of an element than its atomic weight, 

 and, developing the Rutherford theory of atomic 

 ■structure, identifies the Moseley number with the 

 -value of the charge on the nucleus of the atom. 

 He is then able to give an explanation of the 

 nature of isotopes and of the periodic classifica- 

 tion. A description of Aston 's mass spectrograph 

 for the investigation of the isotopes of ordinary 

 'elements is given in an appendix. 



The book is, on the whole, well written, and 

 the matter has been carefully limited to the 

 essential facts and their explanation on the nuclear 

 theory. Full references are given to the original 

 -papers. 



Relativitdtstheorie und Erkenntnis Apriori. By 

 H. Reichenbach. Pp. v-f-iio. (Berlin: Julius 

 Springer, 1920.) 14 marks. 

 The author states that the theory of relativity 

 contradicts the critical philosophy of Kant, 

 An reference both to the concept of time and to the 



NO. 2697, VOL. 107] 



relation of physical fact to Euclidean geometry. 

 There are only two possibilities, he says : either 

 the relativity theory is false, or the philosophy of 

 Kant needs amending at the points at which it is 

 in contradiction with Einstein, The first possi- 

 bility seems ruled out after the brilliant success of 

 the relativity theory, both in its double confirma- 

 tion in experience and in its theoretical contribu- 

 tion to physical thought. Accordingly, the author 

 sets out to analyse the exact point at which it 

 is at variance with critical philosophy, and 

 finally claims to carry through such a modification 

 of the concept "a priori " that the conflict is re- 

 solved. His conclusion is: "We can no longer 

 maintain that the idea of ' a priori ' is independent 

 of all experience, but we must hold that ' a priori ' 

 principles alone constitute the world of experi- 

 ence." This book will repay reading by those who 

 are specially interested in the philosophical aspects 

 of the relativity theory. 



Les Etoiles Simples. By Dr. F. Henroteau. 



(Encyclopddie Scientifique : Biblioth^que 



d 'Astronomic et de Physique Celeste.) Pp. 



xi + 244. (Paris : Octave Doin, 192 1.) lofrancs. 

 As a guide and index to the great advance in 

 knowledge of the stellar system that has 

 taken place in the last thirty years, this volume 

 will be found extremely useful. Commencing with 

 constellations and star-catalogues, the author pro- 

 ceeds to spectral types and schemes of evolution, 

 notably the giant and dwarf hypothesis that 

 holds the field at present. 



The chapter on photometry contains a full descrip- 

 tion of the photo-electric cell, with instructions for 

 its manufacture. Colour- indices are defined, and 

 systems of colorimetry, both visual and photo- 

 graphic, are explained. 



The great increase in the accuracy of stellar 

 parallax determination due to the photographic 

 method, with various refinements suggested by 

 experience, is described in sufficient detail ; in- 

 direct methods — the spectroscopic of Adams, the 

 moving-cluster method of Boss and others, and the 

 hypothetical-mass method applicable to binaries 

 —are then explained. The remaining chapters 

 deal with proper motions, radial velocities, and 

 stellar distribution. 



The book is wonderfully complete considering 

 its small size. Each chapter is followed by a use- 

 ful bibliography, which will enable students 

 interested in special branches of the subject to 

 carry their researches further. 



A. C. D. Crommelin. 



Psyche's Lamp: A Revaluation of Psychological 

 Principles as Foundation of All Thought. By 

 Robert Briffault. Pp. 240. (London : George 

 Allen and Unwin, Ltd. ; New York : The Mac- 

 millan Co., 1921.) 125. 6d. net. 



There is no doubt excellent matter in this book, 

 but the author's method and dogmatic manner are 

 likely to be very irritating to the inquiring student. 

 As the title indicates, the appeal is rhetorical 

 rather than scientific or logical. 



