I)IsrHAH(JH OF KLKCTHKITY. 



24!) 



:ibl('. At the liigiiest pressure at wiiicli the (lisciiaruc passed it took 

 the loiiu of a tliiu ring roiuul the iui<hUe ot A; as the i)ressare i-ot 

 h)\ver and lower the discliarse broadened out, and at very low i)ressures 

 lonned for the .ureater part of its eonrse two separate rings which ran 

 log-ether in the space between one side of the sphere and the tube. 



On file effect prodneed by vonduciors near the discharge tube. — The 

 intensity of the discharge is very much alfected by the preseiu-e of con- 

 ductors in the neighborhood of the discharge tube, especially conductors 

 which have large capacity or which are connected to earth. Let us 

 take, for example, a very simple case, that of a bulb surrounded by a 

 lu'imary which is connected to earth; in this case the approach of the 

 hand, or any conductor connected to earth, will make the discharge 

 Innghter and at the sanu' time less well-detiiied at the edges; touching 

 the tube, thimgli this is already connected to earth, produces a very 

 marked effect in increasing the facility of the discharge. We can, I 

 think, understand the reason of this if we consider the behavior of the 

 tubes of electrostatic iudn(;tion. When the spark passes, these tubes 

 (see Fig. 2, j). 284) rush out from the jars and make for the primary; in 

 their Journey to the primary they pass thiough the bulb and produce the 

 discharge. Let us snp])ose now that there is a large conductor situated 

 somewhere near t]iel)ulb; the tubes, as before, rush from the jar to the 

 primary, but in doing so s<»me of them strike against the conductor; 

 the tubes which do so lose the i)ortion inside tlu^ conductor, ac(piire 

 two ends each on the surface of the conductor, and swing round until 

 they are at right angles to its surface; they remain momentarily 

 anchored, as it Avere, to the conductor, and if th(^ coiiductar is in the 

 neighborhood of the bull), they will in general help to increase the 

 maximum density of the tubes passing through the bulb. Though 

 these tubes may not approximate to closed curves, and so directly i)ro- 

 duce a ring discharge, th«\v ni:iy readily facilitate- tliis discharge indi- 

 rectly; for even those tubes which go radially through the bulb may 



