460 Scientific Intelligence. 



of the electrometer (with very light needle) were observed at 

 intervals of half a minute: Charge + , 14*4, 10*5, 6"5, 3-4 ; time 

 rate 7-5. Charge—, 21-5, 20*0, 18-2, 16-2, 14-2, 12-2 ; time rate 

 4-0. Charge + , 18-3, 14-5, 10*4, 6-7, 3*3, -9; time rate 7-6. The 

 surprising result is thus obtained that the electric current is con- 

 stant while the initial charge of the inner coating of the con 

 denser (the outer being earthed), at nearly 20 volts, gradually 

 quite vanishes. 



In explanation it may be assumed either that the number of 

 ionized nuclei at constant ionic velocity varies inversely as the 

 potential difference, or far more simply, it seems to me, that the 

 velocity of the nuclei is independent of the potential gradient, 

 each nucleus retaining its own specific velocity in the presence or 

 the absence of an electric field, while the number of nuclei is 

 appreciably constant — the point of view taken in my earlier work 

 (Smithsonian Contributions, 1901). The difference of current for 

 positive and negative charges follows from the known excess of 

 negative nuclei. The initial ionization is of the same order as 

 that of the phosphorus emanation. 



12. Handhuch der Spectroscopie ; by H. Kaysek. Yol. ii, 698 

 pp., 4 tables, 57 figs. (Leipzig, S. Hirzel). — The appearance of 

 the second volume of this work gives further assurance of the 

 thorough treatment of the whole subject of spectroscopy which 

 we may expect from this eminent worker in the field. In the 

 present volume, the first chapter is devoted to emission and 

 absorption, with the history, development and proofs of Kir- 

 choff's law. The chapter on radiation of solids furnishes an 

 exhaustive discussion of the various laws which have been formu- 

 lated connecting the emission with the absolute temperature, the 

 distribution of the energy in the spectrum, and the attempts to 

 appl}^ the results in the measurement of temperature. IJnder 

 radiation of gases, the sources of energy and the production of 

 ether vibrations in general are discussed. This is followed by a 

 detailed treatment of the spectra of compounds and of the differ- 

 ent spectra given by the same substance under varying con- 

 ditions. The succeeding chapters deal, respectively, with the 

 influence of pressure, temperature and the nature of the electric 

 discharge upon spectra ; the appearance of spectral lines, their 

 broadening, and reversal ; Doppler's principle and its applications, 

 in the discussion of which the author has been assisted by Dr. H. 

 Konen ; the general relations w^hich have been discovered among 

 the lines of the spectra of individual elements and of those of 

 Mendeleeff's groups. The concluding chapter brings up to date 

 the work which has been done upon the vibrations of light in the 

 magnetic field. Prof. C. Runge has assisted in the development 

 of the Zeeman-effect in accordance wdth the modern ionic theorj^ 



Evidently no effort has been spared in making the references 

 to the literature of every subject discussed as complete as possi- 

 ble up to 1901. The volume is replete with suggested problems 

 of research, to stimulate which is one of the purposes which the 

 author hopes the book may serve. d. a. k. 



