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through the primary coil was reduced to 0:52 of my unit, 
the machine worked, though feebly, and the light was pale 
and cylindrical, without a trace of stratification anywhere. As 
the current was increased, the outline of the light became 
elliptic, but no bands were visible ¢i// the current = 1:51, and 
then only a few at the positive ball. With the full current 
= 3°60, they were brought out in perfect development. It 
deserves to be remarked, that when the lower ball is positive, 
the central light almost touches the other ball; but when the 
current is reversed, there is the usual dark interval at the 
negative. The glass of this egg is thick, and very fluorescent, 
and absorbs completely the few rays of high refrangibility 
which are produced in the hydrogen vacuum, so that none of 
the tests are affected outside. 
«3. Occasionally I use a Smee’s battery of six cells, with 
plates the same size as my Groves. It is, however, very infe- 
rior to Grove both in power and constancy, the six not giving 
as strong a current with the Ruhmkorff as one of the others. 
Connecting it, when excited by them with a receiver in which 
was a hydrogen vacuum = 0:08, the meniscoid strata were at 
Jirst very distinct, but faded away in a few seconds. The 
lower electrode was a point, the other an inch ball, in which 
there was a hole about 45° from its stem. Out of this darted 
a curious funnel of pink flame, passing through the interior 
envelope and the dark shell which surrounded it, and spread- 
ing itself into the exterior brighter one. When only the ex- 
terior terminal of the Ruhmkorff is connected with the upper 
ball, the light is faint and without stratification: the ball has 
the two envelopes with the dark interval, which cease at its 
equator, and this whether it be positive or negative. 
“4, In strong contrast to this is the powerful develop- 
ment of stratification, when there is passed through the hy- 
drogen vacuum 0:07 the current of two Ruhmkorffs, excited 
by a triple Grove, and, as Foucault proposes, connected by 
their interior terminals and their exterior terminals, oppositely 
