786 



SCIENCE. 



[N. S. Vol. XXII. No. 572. 



through Gases ' is Johannes Stark's ' Die 

 Elektrizitat in Gasen ' (Barth, 1902, Leipzig, 

 pp. 1-509) — a book which might have vied in 

 value to the physicist with Thomson's had it 

 not been rendered well-nigh worthless for ref- 

 erence purposes by the slovenly, unscientific 

 and thoroughly un-German way in which ref- 

 erences to original articles have been- inserted. 

 Like Thomson's book, it covers the whole field 

 of gaseous ionization, whether produced by 

 Becquerel or Roentgen rays, by light, by heat 

 or by electric fields. It exhibits immense 

 reading and profound scholarship. It is, in 

 fact, a magnificent compendium of all the 

 facts of gaseous conduction known at date of 

 writing; but, unfortunately, these facts are so 

 badly mixed up with the author's inferences 

 from them that it is in general qtiite impos- 

 sible to tell what is fact and what is infer- 

 ence. It is of the utmost importance that a 

 scientific book, and particularly a book cover- 

 ing a new and speculative field should ac- 

 company each statement of fact with a 

 statement of authority as is so admirably 

 done in both Thomson's and Rutherford's 

 recent books. The bewildering mass of ref- 

 erences to original articles which Stark gives 

 in connection with each general division 

 of his book is practically worthless, because 

 it is obviously impossible to search through 

 all of them in quest of the verification of 

 some particular statement of fact. In a 

 word, then, a book which, with a little more 

 labor and a little better arrangement, might 

 have been an authoritative reference book 

 'i for the physicist in a new field, is, instead, 

 an elaborate and, on the whole, decidedly 

 dogmatic presentation of one man's interpre- 

 tation of recent discoveries — an interpretation 

 which is in many instances questionable, and 

 in some instances certainly erroneous, notably 

 in its relation to induced radio-activity, the 

 stumbling-block of most of the continental 

 physicists. It is, nevertheless, a suggestive 

 and valuable book for the student whose read- 

 ing and discernment are wide enough to en- 

 able him to take at their proper worth its ex- 

 cathedra statements. 



Turning now to books of more limited scope, 



but still books written primarily for the phys- 

 icist rather than for the general public, Ruth- 

 erford's inimitable work on ' Radio-activity ' 

 (Cambridge University Press, 1904, pp. 1- 

 397, and presently to appear in enlarged and 

 revised form) should unquestionably be given 

 first place. Since it is to Rutherford that the 

 credit for the discovery of the real nature of 

 radioactivity is almost wholly due, the subject 

 having been in a state of hopeless confusion 

 till he brought order out of chaos, his book 

 will probably always^ stand as the most impor- 

 tant contribution which this branch of the 

 physics of the electron will ever receive. Al- 

 though the author reveals himself in it as the 

 advocate of a theory, he, nevertheless, never 

 jumbles fact and theory as Stark does. In 

 immediate connection with every assertion of 

 fact is found a reference by which the asser- 

 tion may be checked. From the standpoint 

 of the serious and trained student of radio- 

 activity the book is well-nigh above criticism, 

 for it gives: (1) complete and convenient 

 references to the whole literature of the sub- 

 ject; (2) a clear account of the methods used 

 in the study of the subject; (3) a resume of 

 all the facts discovered to date; (4) a clear 

 discussion of all these facts in the light of the 

 disintegration hypothesis. With suitable re- 

 vision this book will doubtless long be regarded 

 by the student of radio-activity as his diction- 

 ary of the subject. Furthermore, since mathe- 

 matical processes play a much less prominent 

 role than in Thomson's book, and since the 

 style is particularly lucid and interesting, 

 even the general reader will find both interest 

 and profit in its perusal. 



A fifth book which every physicist should 

 take an hour or two to read is a small volume 

 of sixty-two pages by H. A. Lorentz, just 

 issued (1906) by Julius Springer in Berlin, 

 and entitled ' Ergebnisse und Probleme der 

 Electronentheorie.' It is a very unpreten- 

 tious book, being only the publication of a 

 lecture delivered before the Berlin Electro- 

 technical Society. It contains, however, the 

 first attempt with which I am familiar at a 

 semi-popular treatment of the electron theory 

 in its relation to metallic conductors, a subject 



