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white light surrounded by a green atmosphere.» When the 
negative ball is removed, and a dise of varnished card, 2 inches 
diameter, screwed in its place, with the point projecting in its 
centre; a sheet of light spreads over the disc, doubling round it 
and enwrapping the stem. It is remarkable that whatever 
forms the dark bands, is effective here, covering the disk with 
bright rings, which, when the eye is in its plane, look like a suc- 
cession of waves. Inall these cases the stream, as was shown by 
Eisenlohr, is rich in those rays which produce Stokes’s fluores- 
cence ; drawings or writings made on paper with acid solution 
of sulphate of quinine, which are invisible in common light, 
gleam out intensely white on a purple ground; and ornaments 
of Uran glass look strangely bright. Even the glass of the 
receiver becomes luminous under their influence. Sometimes, 
however, this does not occur, and the light of the stream is 
livid ; in this case it will be found that oil from the collar of 
leather has been decomposed by the discharge. Of these 
phenomena the most notable are the rotation of the light, the 
dark bands, the discontinuity of the light near the negative 
terminal, its separate luminous envelopes, the anomaly of com- 
bustion taking place there rather than at the positive terminal, 
and the extraordinary quantity of fluorescent rays. ‘These last 
might be supposed essentially inherent in the electric light ; 
but it will be seen that they are due to the special character 
of the medium. 
‘¢2, Introducing into the receiver a morsel of blotting 
paper moistened with distilled water, the gauge could not be 
got below 0:4. The column of light was much narrower and 
brownish red; there were no bands which I could see, and 
scarcely a trace of fluorescence. The powerful effect of 
watery vapour in thus modifying the appearance of the dis- 
charge indicated the necessity of completely drying any gases 
experimented on, which was in all other cases but one effected 
by enclosing in the receiver a vessel exposing 8 square inches 
of sulphuric acid, and letting it absorb for twenty-four hours. 
