Intelligence and Miscellaneous Articles. 79 



oxygen is positive even at the highest rarefaction, but hydrogen 

 is negative. Air, aqueous vapour, sulphur, and phosphorus vapour 

 appear, when pure, to be excited positively, but more feebly than 

 ox V gen ; mei"cury, on the contrary, appears to be indifferent. The 

 products of decomposition of fatty vapours, which, from using 

 greased stopcocks and connexions, penetrate into the receiver of the 

 mercuiy-pump, acquire stronger negative charges than hydrogen. 

 By continued action of the ignited wires the deportment of the 

 rarefied gases, as well as of the wires, varies, especially if they are 

 thinner than 0"2 millim. ; their molecular structure is altered by 

 continuous ignition. 



The nature of the electrodes is of small influence ; in like manner 

 the occlusion of gases by wires, as well as the detachment of solid 

 particles during ignition, appears to play no essential part. Only 

 by using ignited carbon threads does the disengagement of the gases 

 absorbed by the carbon come into play ; incandescent carbon-fila- 

 ments in a glow-lamp always electrify negatively the residues in the 

 surrounding medium. 



Incandescent platinum-iridium, palladium, and iron wire do not 

 differ essentially from platinum wire. 



The electromotive force is further dependent on the action of 

 extraneous magnetic forces. In rarefied hydrogen it is influenced 

 by the occurrence of Hall's phenomenon ; the existence of which 

 could not be shown with the same certainty in oxygen. In the 

 latter gas the magnet produces in general an increase of the 

 positive, in hydrogen, acting in the same direction, a decrease of 

 the negative, electrifications up to the change of siga ; at the same 

 time the position of the poles exerts some infiuence. 



The phenomena of unipolar conduction display themselves in 

 rarefied gases like those of normal density ; that electricity is 

 always more easily discharged whose sign is opposed to that excited 

 by the process of ignition in the gas. In the magnetic field the 

 conductivity of the gas in contact with the ignited wire increases 

 for negative electricity ; here also the position of the poles has a 

 determining influence. 



The authors attempt to bring the results of their investigation 

 in agreement with Schuster's theory of the electrolytic conductivity 

 of gases, and under the influence of a dissociation of the gaseous 

 molecules at the ignited body. 



In conclusion the authors point to the connexion of their inves- 

 tigations with those of Goldstein and Hittorf on the passage of 

 electricity through rarefied gases using ignited electrodes, and 

 ascribe the results of the experimenters in question to the electro- 

 motive force which occurs at the ignited wire. — Sitzungsberichte 

 der Wiener Akademie, October 23, 1888. 



ON THE PHYSICAL PROPERTIES OF THIN SOLID LAMINA. 

 BY G. QUINCKE. 



The common boundary of two liquids has the tendency to 



