The tube was filled with mercury and inverted over a cup of mercury.
Being 30 inches long up to the bottom of the expanded portion, or lamp
globe, the mercury fell below this and left a Torricellian vacuum there.
One pole of the battery, or dynamo-machine, was connected with the
mercury in the cup, and the other with the upper wire. The stick of
carbon glowed brilliantly, and with perfect steadiness.
I subsequently exhibited this apparatus in the Town-hall of Birmingham,
and many times at the Midland Institute. The only scientific difficulty
connected with this arrangement was that due to a slight volatilization
of the carbon, and its deposition as a brown film upon the lamp glass;
but this difficulty is not insuperable.--_Knowledge_.
* * * * *
ACTION OF MAGNETS UPON THE VOLTAIC ARC.
The action of magnets upon the voltaic arc has been known for a long
time past. Davy even succeeded in influencing the latter powerfully
enough in this way to divide it, and since his time Messrs. Grove and
Quet have studied the effect under different conditions. In 1859, I
myself undertook numerous researches on this subject, and experimented
on the induction spark of the Ruhmkorff coil, the results of these
researches having been published in the last two editions of my notes on
the Ruhmkorff apparatus.
[Illustration: FIG. 1]
These researches were summed up in the journal _La Lumiere Electrique_
for June 15, 1879.
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