80 Prof. A. Welmelt on the Discharge of 



opposite amount for the reverse direction ; or, if we set for 

 a match in the one system, the other system would show a 

 change in phase of 0*3 x 10~ 4 \-f-2, which is seven times the 

 required effect 10~~ 4 , the aberration constant. With con- 

 densers larger than needed for the optical condition, 50,000,000 

 oscillations have been obtained. Thus 



3 X 10 8 M 



iL_ 2x0-5 xlO«~ 3M? 



a distance small enough to allow a rotating mount for the 

 system. Higher frequencies are undoubtedly possible; so 

 that, if the above optical sensibility is not attainable, we can 

 still use a rotating support, with a reduction in this factor of, 

 say, ten times. This method thus contains the requisite con- 

 ditions, if all the experimental difficulties in connexion with 

 the uniformity of the oscillation and the source of light can 

 be overcome. The present stage of the work seems to warrant 

 this conclusion. 



Physical Laboratory, 



University of Nebraska, Lincoln. 

 April 26, 1905. 



X. On the Discharge of Negative Ions* by Glowing 

 Metallic Oxides, and Allied Phenomena. By A. Wehnelt f. 



IN* a recently published paper % Mr. Owen has investigated 

 the emission of negative ions by glowing Nernst burners 

 both at atmospheric pressure and in vacuo. As some time 

 previously to the publication of Mr. Owen's paper I had, in 

 two articles, investigated the discharge of negative elec- 

 tricity by metallic oxides, among which were the oxides 

 composing Nernst burners, perhaps I may be permitted to 

 present here a short account of my experimental results. 

 For details and fuller bibliographical references, the reader is 

 referred to the original articles. 



I. Emission of Negative Ions by Glowing Metallic 

 Oxides at Atmospheric Pressure, 



The metallic oxides to be investigated were in each case 

 supported by carefully cleaned platinum wires of the same 

 length and thickness, which were in turn fixed along the 

 axis of a hollow brass cylinder. The wire and cylinder were 

 enclosed in a glass tube to prevent convection currents of air. 



* Negative ion = electron = corpuscle. 



t Communicated by the Author. Cf. A. Wehnelt, Sitzungsber. der 

 physik.-medicinischen Soc. Erlangen, pp. 150-158 (1903) ; Ann. der 

 Physilc, xiv. pp. 425-468 (1904) ; Verhandl. d. Deutsch. physik. Gesellsch. 

 v. pp. 255-258 & pp. 423-426 (1903). 



% G. Owen, Phil. Mag. viii. pp. 230-257 (1904). 



