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electric. This arrangement gave in air dense sparks 0'*8 long. 
The appearances were very fine. A few of the menisci near 
the positive ball were 0'2 broad, and did not fine away at 
the edge as much as usual. 
‘5, Wishing to prevent the diffusion of the luminous 
stream, I screwed on the point a disc of gutta percha, of such 
size as to touch the glass. With air vacuum 0:05, and Smee, 
when the point was positive, a few menisci were occasionally 
seen near it; but when a hand was brought near the receiver, 
they were much more strongly developed towards it. When a 
Leyden jar (each coating about a foot) was connected with the 
terminals, the stratification was well seen in each direction of 
the current. With the two Ruhmkorffs combined, and three 
Groves in series, the effect was magnificent : all the distance 
from the point to an inch from the ball was covered with 
bright yellowish-green menisci: the envelopes of the ball 
were broad, and the cone of pink light from the hole already 
mentioned dazzling. Reversing the current, the outer enve- 
lope of the point sent several bright streams round the gutta 
percha, which partly fused it. With air vacuum 0:10 the 
appearances were less intense; the stratification reached only 
half way, and the envelopes of the negative ball were not one- 
fourth of their previous bulk. 
*¢6. The destruction of the gutta percha made me replace 
it by a disc of plate glass 3‘ diameter, with a small hole 
drilled in the centre. To this is cemented a tube of gutta 
percha, which slips on a wire screwed in the pump-plate, 
whose point projects 0'-1 above the glass. This arrangement 
gives beautiful results. With air vacuum 0%:07, and Smee, 
when the point is positive, on first passing the current the 
menisci appeared at the dark space near the ball, then in a 
few seconds travelled down the column of light, like waves 
from a stone thrown into water, and when they reached the 
point, disappeared. Ifthe ball was positive, the column of 
light had an elliptic envelope reaching to the dark part. Be- 
