﻿Intelligence and Miscellaneous Articles. 159 



If the polarizing apparatus is turned while at the same time the 

 strength of the current is measured at the galvanometer, two 

 maxima and two minima are observed in the course of a single rota- 

 tion. The minima occur when the plane of polarization of the light- 

 is parallel to the plane of incidence of the rays on the kathode ; the 

 maxima are in positions at an angle of 90° with them. The ratio 

 of maxima to minima is about 10 : 1. If while the plane of 

 polarization is parallel to the plane of incidence, a quartz plate 

 about 2 millim. thick, cut at right angles to the optical axis, is 

 placed in the path of the polarized light, the current increases 

 about sevenfold, corresponding with the rotation of the plane of 

 polarization due to the quartz, When the plane of polarization is 

 at right angles to the plane of incidence, a quartz plate has the 

 opposite effect ; the strength of the current diminishes, as was to 

 be expected, in a corresponding ratio. Apart from a slight en- 

 feeblement of the current due to the loss of light caused by its 

 interposition, a clear glass plate has no effect in either position. 



According to the investigations of MM. Trouton ('Nature,' 

 vol. xxxix. p. 393), Klemencic (Wiedemann's Annalen, vol. xlv, 

 p. 77), and Kighi {Rend, delta R. Ac. dei Lincei. vol. xi. p. 161) it 

 must be taken for granted that, in Hertz's rays of electrical force, 

 the plane of polarization is at right angles to the direction of the 

 electrical displacement. If the motion in the light rays is re- 

 garded as analogous, the result of the experiments described would 

 be thus expressed. 



The luminous electrical current attains its maximum when the 

 electrical displacements in the luminous ray take place in the 

 plane of incidence, its minimum when they are at right angles 

 thereto. In the former case the electrical vibrations contain a com- 

 ponent normal to the kathode, but not in the second. We might 

 be tempted to seek in these changes of potential normal to the 

 kathode, and induced by the electrical rays, the force which impels 

 the negative electricity to leave the kathode. Whether this sug- 

 gestion is correct, can perhaps be ascertained by further experi- 

 ments on the dependence of the luminous electrical action on the 

 angle of incidence of the polarized light, and their connexion with 

 the quantities of light reflected from and retained by the kathode. — 

 Berliner Berichte, February 8, 1894. {Communicated by the Authors.) 



ON VORTEX MOTIONS IN AIR. BY G. QUINCKE. 

 At the meeting of the Natural History and Medical Society of 

 Feb. 7, 1890, I discussed the motion of falling spheroids of oil 

 in water, the specific gravity of which was increased somewhat 

 by the addition of chloroform. Such a spheroid falls vertically 

 in water at rest. But if two spheroids of oil fall simultane- 

 ously close to each other, they approach and recede from each 

 other in falling. The path and the time of fall depend on the dis- 

 tance apart and the velocity of the falling spheroids. This peculiar 

 motion is caused by the vortices which are produced by the 

 falling spheroids of oil in the water about them, which had hitherto 



