DISCHARGE OF ELECTRICITY. 251 



IVo(|iieiitly met with cases where the [)reseMce of a conductor diminishes 

 the intensity of the discharge. One of the most striking of these is 

 when the two jars are iusnlated, and a square discharge tube used. 

 The si)ark was adjusted so that the discharge just, but only just, went 

 round the tube. A spliere connected to earth was then moved round 

 the discharge tube; in some positions it increased the brilliancy of the 

 discharge, and the tube became quite bright, while in other positions 

 it stopped the discharge altogether. 



The observation of the behavior of the discharges through these 

 tubes is a very convenient method of studying the effect of conductors 

 in deflecting the flow of the tubes of electrostatic induction which fall 

 upon them; for the appearance of the discharge is affected not merely 

 by the average, but also by the maximum value of the electro-motive 

 intensity which produces it. Thus a high maximum value, lasting only 

 for a short time, might produce a discharge, while a more equable dis- 

 tribution of electro- motive intensity having the same average value 

 might leave the tube quite dark. 



1 have employed these discharges to study the behavior of bodies 

 under the action of very rapid electrical oscillations in the following 

 way: In the primary circuit connecting the outside coatings of the jar 

 two loops, A and B (Fig. 15), were made, in one of 

 which, A, an exhausted bulb was ])laced, the spark- 

 length and the pressure of the gas on it being ad- 

 justed until the discharge was sensitive, /. c, until 

 a small alteration in the electro-motive intensity 

 acting on the bulb produced a considerable effect 

 upon the appearance presented by the discharge. 

 The substance whose behavior under rapid elec- 

 trical vibrations was to be examined was placed in 

 the loop J5. The results got at flrstwere very per- 

 plexing, and at flrst sight contradictory, and it was some time before I 

 could see their ex])lanation. The Ibllowing are some of these results: 

 When a highly exhausted bulb was ])]aced in B a brilliant discharge 

 passed through it, while the discharge in A stopped. A bulb of the 

 same size, lilled with a dilute solution of (^h'ctrolyte, i)roduce(l noa])pre- 

 ciableettect; when iilled wirha strongsolntioii it dinnned the discliarge 

 in A, but not to the same extent as the exhausted bulb. A piece of 

 brass rod or tube inc^reased the brightness of the discharge in A; oii 

 the other hand, a similar piece of ii'on rod or tube stoi)pe(l the dis- 

 charge in A at once. The most decided effect. Iiowever, was pidduced 

 by a small crucible made of })lnmbago and clay: this, wlien put in the 

 loop B, stopped the <lischaige in A com})letely. 1 found however that 

 by considering the work si)ent on the substance placed in B, tiie pre 

 ceding results could be exi)lained. When a large amount of wori< is 

 spent in 1>, the dis(;harge in A will be dimmed, while no api)reciable 

 effect will be produced on A when the work spent in B is small. Now 



