Miscellaneous Intelligence. 249 



SCIENTIFIC INTELLIGENCE. 



I. Miscellaneous Scientific Intelligence. 



1. Longitudinal Light. — The experiments of Lenakd and 

 Rontgen have awakened great interest in the question whether 

 the cathode rays indicate a periodic movement in the direction of 

 the propagation of the electro-magnetic waves sent out from the 

 cathode. G. Jaumann states that he is the first to maintain that 

 the manifestations of cathode rays support the hypothesis of 

 longitudinal waves. He calculates that the order of magnitude of 

 the time of swing of the cathode rays is from 10~ 8 to 10 -9 sec- 

 onds. E. Wiedemann, on the supposition that the cathode rays 

 are a manifestation of ultra violet light, attributes to them a time of 

 vibration of from 10~ 15 to 10" 16 seconds. Lenard attributes to 

 the rays wave lengths of the order of magnitude of molecules. 

 Jaumann reviews the experimental evidence in favor of the 

 hypothesis of longitudinal waves and finds it of great weight. 

 He then turns to the equations which express Maxwell's electro- 

 magnetic theory of light, and points out that the longitudinal 

 wave, in the direction of the movement of the wave-point, is not 

 expressed by these equations, and that they do not embrace the 

 phenomena which are observed in rarified gases. On the suppo- 

 sition, however, that the dielectric constant and the magnetic 

 permeability of the medium change in value during the instant of 

 propagation, he is enabled to embrace in these equations the 

 hypothesis of longitudinal waves. The paper is of much interest 

 in view of the late development of the subject of cathode rays. 

 — Ann. der Physik und Chemie, No. 1, 1896, pp. 147-148. 



J. T. 



2. The Natural History of Aquatic Insects ; by L. C. Miall. 

 (London and New York, 1895. Macmillan & Co.) — Professor 

 Miall here gives us an excellent example of a kind of work too 

 rarely seen, the popular and yet strictly scientific treatise on nat- 

 ural history. The short introductory chapter treats briefly of 

 some essential matters relating to aquatic insects in general, such 

 as the dominance of insects, their invasion of the waters, adapta- 

 tion to aquatic conditions, the surface-film of water, etc. The 

 rest of the book is devoted to descriptions of the structure, trans- 

 formations, and habits of a series of typical species well appor- 

 tioned among the different groups of insects. Although the 

 species described are European, they are so closely related to 

 North American forms that the work will serve as a guide for the 

 American student almost as well as for the European. The 

 numerous illustrations are excellent. s. i. s. 



3. Huxley Memorial. — It is gratifying to learn that the move- 

 ment to establish a permanent memorial to the late Professor 

 Huxley has met with marked success. The committee announced 

 in a circular dated Dec. 21, 1895, that the subscriptions up to 



