374 Intelligence and Miscellaneous Articles. 



which Hall chose for observing the phenomenon which he discovered. 

 I also made experiments in which one of the electrodes at the 

 acute angle of the rhomb was not used ; the primary current entered 

 the tube through the other, and divided into two parts, one of which 

 passed through one, and another through the other, transverse elec- 

 trode, and which traversed a differential galvanometer in opposite 

 directions. Here were seen all the phenomena which Eighi 

 observed in metals with the same arrangement. Magnetism pro- 

 duced also another kind of transverse current. The current which 

 traversed the transverse electrodes before the action of magnetism, 

 was increased at that electrode towards which the band of light was 

 driven, and weakened at the other; a transverse current was thus 

 produced in the galvanometer, which had the same direction at that 

 transverse electrode towards which the strip of light was urged, 

 and thus had the same direction as the primary current. It hence 

 changed direction on reversing the field, but not on changing the 

 primary current. 



This latter transverse current was not weaker in tube II. than in 

 tube I., or at all events not materiall} 7- so. It was seen even with 

 the ordinary (Hall's) arrangement with four electrodes, as soon as 

 one of the primary electrodes was put to earth or was imperfectly 

 insulated, for then only one portion of the chief current passed 

 through the second (imperfectly insulated) primary electrode ; 

 another part flowed through the two transverse electrodes and the 

 galvanometer-circuit, which was also imperfectly insulated from the 

 earth. By the latter portions of the current all the phenomena 

 which occur in Bighi's arrangement would be produced. 



As the well known fact that the action of a magnet hinders the 

 passage of the current through G-eissler's tubes, seemed analogous 

 to the increase of resistance of bismuth in the magnetic field, I 

 made an experiment in this direction. The primary current passed 

 simultaneously through tube II. and another Teissier's tube ; 

 without the action of magnetism it divided almost uniformly be- 

 tween the two ; but by the action of the magnetic field the division 

 of the current was altered, as it would be on the law of branch 

 currents, if the resistance in tube II. had been increased tenfold. 

 — Wiedemann's Annalen, vol. xxxi. p. 789. 



SOME EXPERIMENTS ON THE TRANSMISSION OF ELECTRICAL 

 CURRENTS IN AIR. BY J. BORGMANN. 



This paper is to be considered as a preliminary communication, 

 in which the author describes some experiments which he has un- 

 dertaken in order to ascertain the manner in which the electrical 

 current is transmitted through air. 



If one conductor of an electrical machine is put to earth, and the 

 other is connected with an insulated point or flame, and if one end 



