H. V. Gill — Electric Discharge in Geisder Tube*. 4'):; 



caused by the striae reappearing successively at places, each a 

 little in advance of the former position : if the striae ah* 

 reappear at the same position there is no general movement. 

 Strata which are thus unsteady may be rendered steady by 

 adding resistance to the circuit, which alters the period oi 

 dilation. (See J. J. Thomson, " Discharge of a condenser.") 



De la Eue and Muller,* with their battery above referred to, 

 made many experiments on the stratified discharge. With 

 regard to the results of their investigations they say : " . . . 

 These results therefore confirm the conclusion already arrived 

 at from other experiments, namely, that the discharge in 

 vacuum tubes is intermittent : but we do not pretend that they 

 make it manifest that stratification is dependent on inter- 

 mittance."f 



A passage from De la Kive's;); paper is as follows: "In 

 reality whether we use a coil, a battery of cells, a machine, etc., 

 to produce stratification, we have never a continuous discharge, 

 but a series of discharges which succeed each other so rapidly 

 that the discontinuity cannot be detected even by a galva- 

 nometer. But this discontinuity none the less exists, as Sir. 

 Gassiot has shown by using a battery of grove cells at high 

 tension, which, with the same electrodes can give rise at first 

 to stratifications, and later on to an arc when the discharge has 

 become continuous." Wiedemann and Hahlmann§ arrived at 

 the same conclusion. 



Many other passages| might be cited, but we think enough 

 has been said to show that no doubt seems to exist as to the 

 discontinuous nature of the stratified discharge. 



The second fact, concerning the physical condition of the 

 gas at a stratum, is proved by the following passag 



De la Rue wrote some time after the memoirs referred to 

 were published :^f "During our experiments we were struck 

 by the evident plasticity of the strata, whose form at times 

 becomes modified when they meet with an obstacle or are 

 influenced by other causes, as for example the crossing of other 



strata produced by a separate discharge A tube with a 



hydrogen residue gives evidence of this viscosity of a stratum : 

 at right angles is a tube of small diameter; in this tube is a 



* Phil. Trans., pt. 1, vol. clxiv, pp. 55-121. 



f Cf. also Ann. Chim. Phys. [5], xxiv, p 4(31, 1881, where de In R 

 to the exceedingly great number of "intermissions" per second— "of millions in 

 a second." 



% Ann. Chim. Phys. [4], viii. 1864. 



§ Pogg. Ann., cxlv. p. 235 and p. 364. 



|| Cf. Phil. Trans, clxix, p. 88, in which de la Rue and Midler Btate thai a \ ar- 

 ley condenser of 48-8 microfarad capacity was employed will, excellent results in 

 the production of the stratified discharge. The discharge of such a comh- 

 evidently oscillatory. 



^ Nature, xxix, p. 350, 1884. 



