480 Scientific Intelligence. 



seconds respectively. When the bulb was filled with hydrogen, 

 all other conditions being kept the same as before, the time was 

 reduced to about 5 sec. for temperatures of 116°, 125°, and 132°. 

 It is thus seen that hydrogen can be pumped, out about 4 times 

 as fast as air. Gaede says that the limiting value of the vacuum 

 obtainable with the diffusion pump is lower than can be attained 

 by the aid of any pump with mechanically moved parts or even 

 by the method of cocoanut charcoal cooled to — 180° C. The 

 only gas or vapor which is not removed by the diffusion pump 

 itself is mercury vapor, and this can be readily and completely 

 condensed by an auxiliary cooling system having a temperature 

 of — 80° C. or lower. — Ann. d. Physik, vol. xlvi, p. 357, Feb. 

 1915. h. s. u. 



7. Elektrische Spektralanalyse chemischer Atome ; by J. Stark. 

 Pp. viii, 138, 19 figures, and 4 plates. Leipzig, 1914 (S. Hirzel). 

 — This monograph is the outgrowth of a lecture which was 

 delivered by the author, in February, 1914, at the invitation of 

 the philosophical faculties of the universities of Leiden and 

 Utrecht. The text presents a detailed account of the exper - 

 mental and theoretical work which has been done by Stark and 

 others on the separation by electric fields of spectral lines, that is, 

 on the so-called .electric analogue of the Zeeman effect. More 

 specifically, the successive chapters deal respectively with (a) 

 preliminary investigations, (b) methods of experimentation, (c) 

 dependence upon electric field strength of the distance apart and 

 of the relative intensities of the components of resolved spectral 

 lines, (d) electrical analysis of lines of the same series and of 

 different elements, (e) allied phenomena, such as broadening of 

 lines, pressure shift, etc., (f) theoretical investigations, and (g) 

 bibliography of the subject. Since the monograph has been 

 brought up to date by the inclusion of experimental work which 

 has been done since the delivery of the original lecture and which 

 had not appeared in the scientific journals at the time of publica- 

 tion of the present text, and since the whole subject is presented 

 in a consecutive, unified form by the chief investigator in this 

 special field, the book deserves to be considered as an important 

 contribution to modern scientific literature. It will undoubtedly 

 pave the way for future valuable research in its particular domain. 



h. s. u. 



8. Advanced Electricity and Magnetism; by William S. 

 Franklix and Barry MacNutt. Pp. vii, 300, with 217 figures. 

 New York, 1915 (The Macmillan Co.). — In order to avoid the 

 danger of making the study of theoretical physics a purely formal 

 mathematical exercise the authors have laid as much stress as 

 possible on the physical aspect of the subject. The importance 

 which they attach to this fact is emphasized by the following 

 italicized sentence quoted from the preface, namely : — " The 

 character of the treatment in this book has been determined 

 throughout by the desire to keep the student's mind jammed up 

 tight against physical things!'"' To a fairly large extent, the 



