4:6Q Scientific Intelligence. 



trum which are the same bands that J. M. Eder discovered by 

 burning a mixture of ammonia gas and hydrogen in oxygen. 

 Walter believes that the discovery of these bands will be of use 

 in the commercial attempt to oxidize nitrogen by the electric 

 spark. — Ann. der Physik, No. 4, 1906, pp. 874-876. j. t. 



10. Photography of a Radium Crystal by its Own Light. — 

 B. Walter has succeeded in photographing a particle of radium 

 by its own light ; and finds that there is considerable variation of 

 light in different portions of the particle. One portion of the 

 crystal which exhibited very strong light when examined under 

 the microscope showed a rupture of its surface. It seems pos- 

 sible that craters are formed which are centers of atomic con- 

 vulsions. — Ann. der Physik, No. 5, 1906, pp. 1030-1031. j. t. 



11. Ions, Electrons, Cor pu scutes. Memoires r'eunis et publies 

 par H. Abraham et P. Langevln. 2 vols., xvi + 1138 pp. Paris, 

 1905 (Gauthier-Villars). — These volumes, issued by the French 

 Physical Society, contain a collection of papers and extracts from 

 papers, bearing upon the modern theory of the atomic constitu- 

 tion of electricity. This theory forms the basis of most of the 

 work which has made the last decade a memorable one in the 

 history of physics ; it has come to occupy a position of such 

 fundamental importance in many different branches of the science, 

 that the student who is not fairly familiar with its details is at a 

 decided disadvantage. The development of the theory has been 

 rapid, it has been applied to a great variety of problems, and 

 important papers are widely scattered among the scientific period- 

 icals of the world. It thus becomes a matter of some difficulty 

 to gain an adequate knowledge of the present point of view, unless 

 one has been particularly interested in the subject from the first. 



The present volumes will give most useful help in this difficulty, 

 and will prove a great convenience even to those who are familiar 

 with the subject. The selection of papers for reprinting has 

 been made with great care and with admirable judgment. The 

 arrangement is alphabetical with respect to authors, but a well- 

 classified topical index makes it possible to read the papers upon 

 any portion of the subject in a continuous manner. In addition 

 to numerous subdivisions dealing with the different modes of pro- 

 duction of electrons and gaseous ions, and the experimental study 

 of their properties, there is also a series of papers upon the dynam- 

 ics of electrons, with applications to optics, to the phenomena 

 of radiation and metallic conduction. Extensive and important 

 theories, such as those of Lorentz and Larmor, are summarized by 

 the authors themselves with numerous extracts from published 

 papers. 



It would be exceedingly difficult, if not impossible, for any one to 

 write a treatise which would give the reader so broad and so just 

 a view of the state of our knowledge of ions and electrons as do 

 the present volumes. A feeling of reality and intimacy comes 

 from reading the original papers in which important discoveries 

 were announced to the world, which is seldom gained from a 



