429 
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 02 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 dise 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 fased 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 0i-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. If the ball was positive, the column of 
light had an elliptic envelope reaching to the dark part. Be- 
