June 19, 1919] 



NATURE 



?>0?s 



viscosity of fluids, two on light, and one on 

 sound. The exercises are illustrated by half- 

 tones, but as no written description of the ap- 

 paratus is given it is difficult in some cases to 

 guess how the experiment is to be carried out. 

 The student would often be at a loss if guided 

 by these notes alone. H. S. Allex. 



SECRET OR MYSTERY? 



(i) The Secret of Personality: The Problem of 

 Man's Pers07ial Life as Viewed in the Light of 

 an Hypothesis of Man's Religious Faith. By 

 Dr. George Trumbull Ladd. Pp. ix + 287. 

 (London : Longmans, Green and Co., 1918.) 

 Price 75. 6d. net. 



{2) The Philosophy of Mr. B*rtr'^nd R^ssHl. With 

 an Appendix of Leading Passages from Certain 

 Other JVorks. Edited by Philip E. B. Jourdain. 

 Pp. 96. (London : George Allen and Unwin, 

 Ltd., 1918.) Price 35. 6d. net. 



(i) T T is said that the reader of a once famous 

 J- book entitled "The Secret of Hegel" re- 

 marked when he closed the volume that whatever 

 the secret might have been it had been very suc- 

 cessfully kept. No difficulty of discovery is likely 

 to baffle the reader of Dr. Ladd's "Secret of 

 Personality." His secret is an open one, and in 

 the author's genial treatment personality is not 

 mysterious either in the sense of inspiring awe or 

 in that of suggesting occult sources of knowledge. 

 Philosophy itself throws a strange light on man's 

 personality in the attraction it has for us in our 

 youth and in our old age, with the eclipse of 

 interest it undergoes in the stress of active life. 

 So in this little book we feel the professor's keen 

 enjoyment in his old age (he was born in the same 

 year as M. Clemenceau), writing not to instruct 

 us, not to guide us in metaphysical or psycho- 

 logical research, not even to console us, but to 

 give expression to his own reflections on the 

 problems of philosophy. 



(2) Mr. Jourdain 's satire on the work of a con- 

 temporary philosopher will afford much amusement 

 to those who are familiar with that philosopher's 

 method and with the kind of problems to the solu- 

 tion of which he devotes his energy and ingenuity. 

 To those who do not know this work or are un- 

 interested in it, not only will the humour be lost, 

 but the object of the book will also be unintelli- 

 gible. To such it will appear a cryptic puzzle not 

 worth trying to solve. Yet some of the papers 

 are excellent for their logical nonsense, and might 

 themselves be set as subjects for a logical seminar. 

 Particularly good is the one entitled "The Mor- 

 tality of Socrates. " What one cannot help feeling, 

 however, in regard to the whole is that the author 

 satirised is himself endowed with a very abundant 

 fund of humour which makes its presence felt in 

 the most ultra-mathematical and logical disquisi- 

 tions, and many of Mr. Jourdain 's brightest hits 

 are jokes concerning his author's jokes. More- 

 over, a joke prolonged into a book tends to 

 become so serious as to threaten to defeat its 

 intention. 



NO. 2590, VOL. 103] 



OUR BOOKSHELF. 

 Mikrographie des Holzes der auf Java vorkom- 

 menden Baumarten, im Auftrage des Kolonial- 

 Ministeriums. Unter Leitung von Prof. J. W. 

 Moll, bearbeitet von Dr. H. H. Janssonius. 

 Funfte Lieferung. Pp. 337-764. (Leyden : E. J. 

 Brill, 1918.) 



The present part completes the third volume 

 (dealing with the calycifloral section of Dicotyle- 

 dons) of the detailed description of the minute 

 structure of the wood of the tree species occurring 

 in Java. It comprises the families Rhizophorese, 

 Combretaceae, Myrtaceae, Melastomaceae, Lythra- 

 rieae, Samydaceae, Datisceae, Araliaceae, and Cor- 

 naceae, and includes the description of 124 species 

 and varieties. At the beginning of the account 

 of each family are given a list of the literature, an 

 enumeration of the material examined, and a sum- 

 marised description of the general characters of 

 the anatomy of the wood and its constituent 

 elements. Then follow, first, a discussion of the 

 bearing of the results of the investigation on the 

 systematic grouping of the genera and species 

 within the family ; secondly, a table in the form of 

 a key for the determination of the species by 

 means of characters afforded by their wood-struc- 

 ture ; and thirdly, a detailed description of the 

 characters in each species, with a block illustra- 

 tion of the first species described for each genus. 

 The authors have brought together much detailed 

 information on the minute structure of the wood 

 of the species examined, and the work when com- 

 pleted will form a valuable contribution to the 

 systematic study of genera and species from a 

 point of view which hitherto has been insufficiently 

 recognised. 



Molectdar Physics. By Dr. James Arnold 

 Crowther. Second edition. (Text-books of 

 Chemical Research and Engineering.) Pp. 

 viii + 190. (London: J. and A. Churchill, 1919.) 

 Price 65. net. 



The fact that a second edition of Dr. Crowther's 

 little volume has been required so soon shows 

 that the praise given to the first edition in Nature 

 for March 25, 1915, was not undeserved. 

 A complete revision of the material has been 

 carried out, and, in spite of the conditions of a 

 great war not laeing favourable to theoretical 

 research, some additions have been made. In 

 particular, the results obtained in the laboratory 

 of Sir Ernest Rutherford have increased our 

 knowledge of the structure of the atom, and the 

 author has added a special chapter on this pro- 

 foundly interesting subject, while the chapter on 

 the chemistry of the atom has been almost com- 

 pletely rewritten from the point of view of Sir J. J. 

 Thomson's theory of valency and chemical affinity. 

 The complaint as to the absence of an index in 

 the earlier edition has been at least partly met by 

 a subject index occupying a couple of pages. In 

 its revised form it is certain that the book will be 

 well received, and will be read not only by physi- 



