638 REPORT — 1892. 



The phenomena are described wliich occurred in different tubes and in different 

 positions, especially curious dark spaces in the neighbourhood of the condenser's 

 plates in the vacuum tubes, through which the oscillations passed unabsorbed. 

 Some cases were discussed in which the discharges ceased in a singular manner by 

 improving the vacuum. 



The paper is to be published in full in Wiedemann's ' Annalen.' An account 

 of some of the experiments, with an explanation of them, has been published 

 «,lready in the ' Verhandi. der Societas Physico-Medica ' of Erlangen, 1892. 



4. On Primary and Secondary Batteries in which the Electrolyte is a Gas. 

 By Arthur Schoster, F.Ii.8. 



If a current of electricity passes through a vessel which is partially exhausted, 

 the whole gas contained in the vessel becomes a conductor in the ordinary sense, 

 and a single cell will send a measurable current through it. This phenomenon, 

 which may conveniently be called 'secondary conduction,' has been investigated 

 "by the author and Professor Arrhenius. A more detailed study during the past 

 year has brought some interesting phenomena to light. If the secondary electrodes 

 are platinum and the gas is a hydrocarbon, phenomena of polarisation are observed 

 •exactly similar to those found when water is decomposed. The electromotive force 

 of polarisation in that case amounts to about three or four volts. No polarisation 

 or traces only are found with hydrogen, oxygen, nitrogen, cyanogen, aqueous 

 vapour, ammonia, and other gases experimented upon, but phosphoretted hydrogen 

 shows the phenomenon. 



When the electrodes are made of copper or iron no polarisation is observed in 

 hydrocarbons. On the other hand, when aluminum or magnesium is used it 

 rises to very high values. Magnesium electrodes, in wliich the secondary current 

 from thirty Clark cells was allowed to pass for some time, showed a polarisation of 

 35 volts. 



The polarisation effects are studied just as in the case of liquids by interrupting 

 the polarising current and connecting the secondary electrodes with a galvanometer 

 or electrometer. 



When a hydrocarbon is used both electrodes become covered with a thin film, 

 which shows the colours of thin layers of metallic oxides or sulphides. The fact 

 that the electromotive force depends so much on the nature of the metal tends to 

 show that a metallic carbon compound is formed by the action of the primary cur- 

 rent, and that the effects are analogous to those of the secondaiy battery. 



The author has also studied the currents observed when electrodes of different 

 metals are inserted into a gas rendered sensitive by the electric discharge. 

 Arrhenius had already shown that zinc and platinum in air give a permanent 

 difference of potential under these circumstances. The author finds that, whatever 

 the gas which has been converted into a conductor by a primary discharge, perma- 

 nent currents may be obtained from magnesium and platinum electrodes, the 

 magnesium always being electro-negative. The electromotive force is, however, 

 different in different gases, and higher, for instance, in oxygen than in hydrogen. 



5. On the Stability of Periodic Motion. By Lord Kelvin, F.B.S. 



6. The Efficiency of Transformers. 

 By Professor W. E. Ayrton, F.B.S., and W. E. Sumpner. 



7. Note on the Registration of Transformers. 

 By Professor W. E. Atrton, F.B.S., and E. W. Smith. 



