Chemistry and Physics. 63 



that of Robert Alexander Houstoun is entitled Investigation 

 upon the Influence of Temperature on the Absorption of Light in 

 Isotropic Bodies. Miiller gives tables of the extinction-coeffi- 

 cient e in various substances; e is defined by the formula : 



log tan a t — log tan a„ 



in which a, and a„ are angles through which the polarizing appa- 

 ratus must be turned to bring two beams of light passing through 

 two solutions to equal brightness : d is thickness of solution. The 

 method is an interesting one, and the conclusions are important 

 to the student of molecular physics. The chief interest of Mr. 

 Houstoun's paper lies in its bearing on the electron theory. He 

 remarks that it is apparent that the number of electrons with 

 fundamental vibrations per unit of mass changes with tempera- 

 ture in the visible spectrum, and that the simple dispersion 

 theory is extended by a consideration of the wechselseitige forces 

 of the electron. — Ann. der Physik, No. 13, 1906, pp. 515-573. 



J. T. 



8. The Doppler Effect in Caned Streams. — If the cathode in 

 an exhausted tube is perforated with holes 0*5 to l mm in diameter, 

 the so-called canal streams are observed behind this cathode, 

 apparently streaming diametrically opposed to the direction of 

 the cathode rays toward the anode. J. Stark publishes three 

 papers on these canal ray s , entitled, respectively, Light Emission 

 of the Canal Rays in Hydrogen, Canal Rays in Potassium and 

 Sodium Vapor, The Doppler Effect' in the Spectrum of Mercury 

 Vapor. He finds a displacement of certain spectrum lines which 

 he attributes to a change of velocity in the line of sight, and 

 thus substantiates his previous observations on canal rays. Not 

 only is there a displacement, but also a broadening, which is proof 

 to his mind of this Doppler effect — analogous to the change in 

 position of a spectrum line of a star which is either approaching 

 or receding. This Doppler effect has been sought by various 

 observers, but has not been hitherto observed. Si ark discusses 

 at considerable length the conditions of temperature and pressure 

 for the proper observation of this effect, and the broadening of 

 series lines due to this effect. The papers seem very important : 

 but are difficult to- review on account of a certain diffusiveness of 

 style and lack of a summary of conclusions. — Ann. der Physik, 

 No. 13, 1906, pp. 401-470. ' J. T. 



9. Oscillatory Discharge of a Polarized Cell. — F. Krttger, 

 by means of a Helmholtz pendulum, detects oscillatory dis- 

 charges as well "as non-oscillatory discharges of polarized cells. 

 The oscillatory discharges are often concealed, but can arise 

 since the cells have electrostatic capacity and self induction is 

 provided by the leading wires. He quotes Nernst's observations 

 on the analogy between the oscillations of the polarized cells and 

 the movements of a stimulated nerve. The observations are sup- 

 ported by a long mathematical discussion on the diffusion capac- 



