270 



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, in 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 V, 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. 



An electro-magnet is placed at C, and is constructed so as to allow 

 the two helices to be separated ; and by these means the larger vessel 

 can, if required, be placed between them, and any portion of the 

 luminous discharge may be thus exposed to any part of the magnetic 

 field. 



Battery. 



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

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



