Mr. J. P. Gassiot on the Voltaic Discharge in Vacuo. 75 



tions (Phil. Trans. 1839, part 1), describes some experiments madewith 

 seventy series of his constant battery, and states (page 93) " that the 

 arc of flame between the electrodes was found to be attracted and 

 repelled by the poles of a magnet, according as one or the other pole 

 was held over or below it, as was first ascertained by Sir H. Davy ; 

 and the repulsion was at times so great as to extinguish the flame." 



In the Philosophical Magazine of July 1858, Mr. Grove has de- 

 scribed an experiment made by him with one of my vacuum-tubes, 

 2 feet 9 inches long, in which he ascertained that the discharge of a 

 Ruhmkorff's induction coil could be stopped by bringing a magnet 

 near the positive terminal wire, but that this effect was not obtained 

 when the magnet was made to approach the negative. The mercurial 

 vacuum-tube in which Mr. Grove observed this phenomenon was 

 unfortunately shortly afterwards broken ; and although Mr. Grove 

 and myself have repeatedly endeavoured to obtain the same result in 

 similar and in other vacuum-tubes (and since that period I have ex- 

 perimented with upwards of two hundred), all our efforts have been 

 hitherto unsuccessful. 



The experiments I am now about to describe were made with two 

 carbonic acid vacuum-tubes, the vacua being obtained in the same 

 manner as described by me in the Philosophical Transactions, part 1, 

 1859*. 



A, h>the annexed figure, represents a glass tubular vessel (No. 146), 

 24 inches long and 6 inches diameter in its wide part ; at one end, 

 attached to the platinum wire («), is a concave copper plate 4 inches 

 diameter, at the other end is a brass wire attached to the platinum 

 wire (b). B represents a glass tube (196) 5 inches long (in its wide 

 part), in which two small balls of gas-retort coke are attached to the 

 platinum wires a' and b f , and are placed about 3 inches apart, all the 

 platinum wires being hermetically sealed in the glass. In A the 

 potash is placed in the vessel between the electrodes ; in B it is 

 placed in the further part of the tube, beyond one of the wires. 



Battery. 



* The carbon-balls do not in these experiments affect the results described, as 

 1 have obtained the same in a tube of the same dimension with brass wires. 



