1862.] 335 



When sounds are heard, either with the lesser number of cells 

 (2240) or when the overlapping striae of the greater number are 

 spread by the magnet, the discharge is resolved by the mirror, and 

 as such is intermittent ; but otherwise it is continuous. 



Mr. Stewart, Director of Kew Observatory, was present when I 

 made this experiment ; he examined the separation of the discharge 

 by the revolving mirror, and heard the sounds, under the conditions 

 of the discharge which I have described. 



16. No. 320. The discharge in this tube did not pass until the 

 potash was heated, when a faint luminosity appeared, and imme- 

 diately afterwards one, and then two, cloud-like striae came from the 

 positive wire, while round the negative a large brilliant glow was 

 produced ; as the discharge continued, the negative wire became red- 

 hot. I have repeated this experiment many times with the same tube ; 

 platinum from the negative wire is deposited in a lateral direction, 

 on the sides of the tube, as it would have been from the discharge of 

 an induction coil. 



17. No. 315 (Plates I. & II. fig. 7, &c.). With 3360 cells, the 

 discharge in this tube is of a dazzling brilliancy, exhibiting 12 or 14 

 stri&e (Dr. Faraday and Dr. Tyndall, who witnessed this experiment, 

 counted 13) ; that nearest the negative ball, being truncated and of a 

 pale-green colour, impinged on the luminous glow which surrounded 

 that terminal (fig. 13). 



With a resistance of the two columns of distilled water (fig. 1), each 

 18 inches in length, introduced in the circuit ( 10), certain changes 

 in the form and number of the striae take place. Some of these I 

 have endeavoured to represent by figs. 7, 8, 9, 10, 11, 19, and 13. 



The wires attached to the terminals of the battery are placed 

 inside the two tubes containing distilled water, connected with each 

 other from the bottom ; as soon as the wires touch the surface of the 

 water, a faint luminous discharge is observed at each ball of the 

 vacuum-tube. As one wire attached to the negative is slowly de- 

 pressed, the two luminous discharges appear to travel towards or to 

 attract each other ; and at times I have noticed a portion of the 

 positive luminosity to pass over and intermingle with the negative. 



I tried the effect of a magnet on the discharge while in this state ; 

 but it was always extinguished *, and I could not obtain any satis- 

 factory result. 



* Proc. Roy. Soc. Jan. I860. 



VOL. XII. '2 11 



