1862.] 333 



introduced the two tubes a and b, containing the distilled water, in the 

 circuit. I ascertained that, by varying the depth to which the wires 

 attached to the terminals of the battery are plunged in one or both 

 of the tubes containing the water, the resistance could be regulated 

 with great precision, and that it was immaterial in what part of the 

 circuit the vacuum-tube or the resistance was introduced, provided 

 the circuit is completed. 



11. In proceeding to describe the experiments, I may premise 

 that, in using the terms intermittent and continuous as applied to the 

 discharge of the battery, I desire only to denote that when the 

 discharge is examined by a vibrating or revolving mirror, in the 



former the appearance of a series of distinct discharges is plainly 

 perceptible ; in the latter this separation is not seen, but the 

 discharge appears as a continuous light. 



12. No. 248. In this tube, with 2240 series, luminous glows are 

 observed on both balls, that on the negative being larger and more 

 brilliant ; in the dark discharge between the balls no trace of striae 

 can be seen ; but at intervals a flash discharge takes place. The 

 luminous glow on each ball appears as a continuous discharge ; both 

 glows at times flitter, attaching themselves sometimes on one, and 

 then on the opposite sides of the balls ; but even then they are not 

 resolvable by the mirror. 



13. When a resistance of about 3 inches in length, of distilled 

 water placed in the glass tubes a or b ( 1 0) (fig. 1 ), is introduced in 

 the circuit, the discharge assumes the narrow stratified appearance 

 which I described in a similar vacuum-tube*, fig. 2 : the discharge 

 is now intermittent, being separated by the revolving mirror: as 

 the wire is depressed and the resistance thus reduced, the discharges 

 when examined by the mirror are found to be quicker in succession, 

 being less and less separated until we arrive at a point at which the 

 discharge suddenly changes its character, appearing now as a con- 

 tinuous light. Gradually raising the wire, and thus increasing the 

 resistance, the discharge becomes again stratified and intermittent, 

 more or less as the resistance is increased or reduced. 



14. No. 70. This tube contains vapour of iodine ( 9): with the 

 induction coil a luminous discharge is obtained, which exhibits very 

 narrow striae ; with the battery of 3360 cells striae are not observable, 



* Proc. Roy. Soc. June 1860. 



