312 Scientific Intelligence. 



offers great mathematical difficulties. The author is apparently 

 unacquainted with the direct experimental determination of the 

 velocity of electric waves by Professor Trowbridge and Professor 

 Duane, which avoids the mathematical difficulties, and by which 

 a velocity closely agreeing with that of light was obtained. — 

 Wied. Ann., No. 2, 1899, pp. 233-290. j. t. 



7. Polarization and hysteresis in dielectrics. — W. Schaufel- 

 berger employs ellipsoids of paraffine and hard rubber, and 

 studies the damping of their oscillations in the electric field of a 

 Kohlrausch condenser. The mathematical consideration of the 

 motion of the dielectric contains hypotheses drawn from analo- 

 gous phenomena of polarization and hysteresis in the case of iron. 

 It was found that the loss of energy due to hysteresis in paraffine 

 is 2*119 per cent and in hard rubber 63*49 per cent. The latter 

 number is regarded as an approximation. — Wied. Ann., No. 2, 

 1899, pp. 307-324. j. t. 



8. A new method of showing electric waves. — A simple resona- 

 tor devised by Rhigi consisted in a sheet of tinfoil applied to glass, 

 the foil being divided by a fine line. Albert Neugschwender 

 has discovered that if a galvanometer and a battery are 

 placed in circuit with a silver-coated surface divided by a 

 fine line, that the galvanometer will show a deflection due to 

 a Hertzian wave if one breathes on the metallic surface or places 

 a wet sponge near it. The vapor converts the divided surface 

 into a species of coherer. — Wied. Ann., No. 2, 1899, pp. 430-432. 



J. T. 



9. Separation of long waves of heat by means of quartz 

 prisms. — The very important work of H. Rubens and E. 

 Aschkinass on this subject has shown that it is possible by 

 means of quartz and sylvine to isolate waves of heat of great 

 wave-length, since these waves are not absorbed by these sub- 

 stances. The above authors have now entered into a discussion 

 of the further extension of their method. They find that intensity 

 of energy between wave lengths 50/x and 60//. is greater than the 

 whole energy beyond X = 60//,. Since the energy between 50 and 

 60/x is only T g^,o"oT °^ tDe whole amount of energy emitted by 

 the sources employed by them (Auer burner), it does not appear 

 possible to further extend their method. — Wied. Ann., No. 2, 

 1899, pp. 459-466. j. T. 



1 0. Theory of conduction of electricity through gases by charged 

 ions. — Professor J. J. Thomson has reduced his observations 

 upon this subject to a mathematical form, and has obtained equa- 

 tions which embody his experimental results. He explains many 

 of the phenomena observed in Geissler tubes, and believes that 

 the most striking features of the discharge through vacuum tubes 

 are due to the difference in velocity between the positive and 

 negative ions. He points out that a study of the distribution of 

 intensity in Geissler tubes supports the theory of ionization. — 

 Phil. Mag., March, 1899, pp. 253-268. j. t. 



11. The Hall phenomenon and the theory of Lorentz. — Poincare 





