C. GENERAL PHYSICS. 141 



surfaces free from oxides. The positions of the lines in 

 the spectrum were determined by reference to a photo- 

 graphed scale, and it was found that with large angles of 

 incidence the lines in light polarized perpendicular to the 

 plane of incidence were displaced toward the blue end of 

 the spectrum, as compared with those lines that occur in 

 light polarized parallel to the plane of incidence. Again, in 

 the former light a new line occurs in the vicinity of the 

 line T>. With an increase in the index of refraction of the 

 surrounding medium, the lines in the parallel polarized light 

 undergo displacement toward the blue, while those in the 

 perpendicular polarized light alter their positions but very 

 little. In the light polarized parallel to the plane of in- 

 cidence, as also in natural light, the positions of the lines 

 did not vary with the angle of incidence, while they do vary 

 in perpendicularly polarized light. 7 ^4, XLVIII., 232. 



A NEW CLASS OF ABSORPTION PHENOMENA. 



A late number of the memoirs of the Spectroscopic So- 

 ciety of Italy contains a contribution by Lockyer to the 

 spectroscopic investigation of the absorption phenomena. 

 These phenomena consist in observing the absorption pro- 

 duced by vapors of sodium and potassium heated in a red- 

 hot tube through which a beam of sunlight passes. Lockyer 

 states that the Fraunhofer line D becomes broader on one 

 side ; and again, in reference to the general question of the 

 absorption of great thicknesses of metallic vapors, he states 

 that metallic elements of low specific gravity give spectra 

 approaching in their appearance a continuous spectrum by 

 increasing the number of their lines. 3Iemoirs of the Italian 

 Spectroscopic Society ', 1874, 97. 



THE PHOSPHORESCENCE OF PHOSPHORUS. 



From the doctorate dissertation of Joubert, of Paris, we 

 gather that he has definitely settled the question as to the 

 origin of the phosphorescent light of phosphorus by demon- 

 strating that it is really due entirely and only to the slow 

 oxidation of that substance. Anions the numerous results 

 of his unusually thorough and suggestive work, we note that 

 in pure oxygen the temperature at which phosphorescence 

 takes place depends on the pressure of the gas; and in di- 



