UPON ELECTRICAL DISCHARGE PHENOMENA IN RAREFIEL) GASES. 
137 
and coniiectiiig that with the positive knoh of the induction coil or iiiHuence 
machine. 
The plane in which the liiniinous ring appeared was controlled by the position of 
the tinfoil during stimulation. Fig. 2 shows the apj^earance of the ring for tw(j 
respective positions of the tinfoil })atch. On no occasion did a luminous ring form 
when T was placed behind the point of the electrode. Sometimes, when the electrode 
was magnetised, a glowing gas encircled it at an inch or so from the pointed end, and 
this faintly luminous cloud moved I'apidly forward, gaining in iDiiglitness until it 
circumscribed the point itself. Then it slowly faded away. It must be understood, 
however, that this effect was seldom seen, the ring generally appearing to suddenly 
encircle the extremity of the electrode, where it remained visible for some seconds 
unless disturbed by unequal attractions exerted upon it through alterations in the 
electrostatic charges residing, either upon the magnetic electrode (which was insulated) 
or upon the walls of the bull). This effect was more noticeable, however, with the 
apparatus shown in hg. I, fur, in that case, by touching different parts of tlie ludh, 
or by slightly electrifying the electrodes by means of an influence macliine, tlje 
luminous ring coidd be moved backwards or forwards—threaded first on t(.) one 
electrode and then the other—in a manner consistent with tlie view that it was 
mainly composed of a negatively electrified cfjud of gaseous particles. 
IiUcriiiittent Luminosity. 
A stroboscopic examination of tlie ring proved that its luminosity was not con- 
tmuous. The numlier of flashes of light per second also varied from time to time. 
Tlie luminosity of the ring therefore ajipeared to depend iqrni an Intermittent 
discharge occurring within the bulb. 
Residual Oases. 
Ihe nature of the gas in ulilch the ring appeared did nut markedly influence its 
brightness or colour. It must however be pointed out tliat with the apjparatus 
VOL. CXCVir.-A. T 
