431 
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‘<9. Supposing the vicinity of the glass of the receiver to 
the luminous stream might have some effect, I used a larger 
one, 6: internal diameter, and allowing 6: from the ball to 
the glass disc. With Smee and air vacuum 0'-04, the hemi- 
spheres covered the disc, about 40 to the inch, in the stream 
above still closer; but besides these, others were occasionally 
seen, broad, hazy, and not curved, which seemed to move 
rapidly, if the eye was suddenly depressed. These are, pro- 
bably, an optical deception. 
*©10. With hydrogen vacuum and Smee, at 0:70, the 
ball positive, the stream was bright, and covered with fine 
black bands: then it broke into a faint broad one, with lateral 
brushes to the glass, in which no bands were visible. With 
the point positive, the stream was bright, 0'-4 broad, reaching 
05 from the ball, and all covered with fine sharp bands. 
Round it was a faint envelope, into which the bands occasion- 
ally darted out, but only every second or third one. At 0:6 
the bands became hemispheres, covering the whole glass disc, 
full twice as broad as the first set, but worse defined, misty, 
and the intervals not absolutely dark. The mass of light 
ended in a cone, whose point was about 1:5 from the ball. 
«11. I was indebted to Mr. Mallet for the use ofa large 
Ruhmkorff: it was the same diameter as mine, 4‘, but longer, 
in the ratio of 11:5 to 7. It did not give a longer spark in 
air, but a far denser one. Excited by four Groves, hydrogen 
vacuum at 4'-2, the discharge passed in faint ramifications. 
At 1-70 it was a bright ribbon, 0'-25 broad, between green 
and lilac, covered with faint bands, which attained their maxi- 
mum of distinctness at*0'-70. At 0:14 the appearances were 
the normal ones of this vacuum, but finer than I had ever seen 
them. When the ball was positive, the shells wrapped round 
it, and were a little flattened below it on each side of the 
axis. 
*©12. Admitting air and exhausting, the discharge passed 
_ at 2i-70, in bluish branches, filling the receiver. At 11-52 it 
VOL. VI. 2R 
