120 Prof. J. Zeleny on the Ratio of the Velocities of the 



Mr. Rennie, by whom these experiments were made during 

 the recent Christmas holidays, had previously experimented 

 on a platinum plate which had been made the positive pole in 

 an electrolytic cell with an electromotive force of one volt, 

 tending to decompose water acidulated with sulphuric acid ; 

 the other pole being a piece of platinum wire. After the 

 plate had been one hour under this influence in the electro- 

 lytic cell he removed it, and dried it by lightly rubbing it 

 with a piece of linen cloth. He then placed it in the Volta- 

 condenser, and found it to be negative to a platinum plate in 

 ordinary condition ; the difference observed was *27 of a 

 volt. This experiment was made on October 21 ; and on 

 November 8 it was found that the difference had fallen from 

 *27 to '07. Mr. Rennie also made similar experiments with 

 the platinum disc made the negative pole in an electrolytic 

 cell, and found that this rendered the platinum positive to 

 undisturbed platinum to a degree equal to about *04 of a volt. 

 The effect of soaking the platinum plate in dry hydrogen gas, 

 alluded to in my first postscript, which also was observed by 

 Mr. Rennie, was found to be about -11 of a volt. Thus in the 

 case of polarization by hydrogen, as well as in the case of 

 polarization by oxygen, the effect of exposure to the dry gas 

 was considerably greater than the effect of electro-plating the 

 platinum with the gas by the electromotive force of one volt. 



PL] 



VI. On the Ratio of the Velocities of the Tivo Ions produced 

 in Gases by Rontgen Radiation; and on some Related Phe- 

 nomena. By John Zeleny, B.Sc, Assistant Professor of 

 Physics, University of Minnesota*. 



IT is the object of this paper to show that the positive and 

 negative ions, which take part in the conduction of gases 

 exposed to Rontgen rays, move with different velocities when 

 in the same electric field ; to determine the ratio of these 

 velocities in several gases ; and to consider various phenomena 

 which are consequences of or are affected by the difference in 

 the two values. 



The subject matter will be treated under the following sub- 

 divisions : — 



§ 1. The method for determining the ratio of the two 



velocities. 

 § 2. The apparatus used. 

 § 3. The form of tube used for constancy of radiation. 



* Communicated by Professor J. J. Thomson. 



