We might, then, perhaps
explain the different effects of the wear of the carbons serving as
rheophores, according as the currents are continuous or alternating, by
the different calorific effects produced on these carbons, and by the
effects of electric conveyance which are a consequence of the passage of
the current through the arc.
We know that with continuous currents the positive carbon possesses a
much higher temperature than the negative, and that its wear is about
twice greater than that of the latter. But such greater wear of the
positive carbon is especially due to the fact that combustion is greater
on it than on the negative, and also to the fact that the carbonaceous
particles carried along by the current to the positive pole are
deposited in part upon the other pole. Supposing that these polarities
of the carbons were being constantly alternately reversed, the effects
might be symmetrical from all quarters, although the only current
traversing the break were of the same direction; for, admitting that the
reverse currents could not traverse the break, they would exist none the
less for all that, and they might give rise (as has been demonstrated
by Mr. Gaugain with regard to the discharges of the induction spark
intercepted by the insulating plate of a condenser) to return discharges
through the generator, which would then have, in the metallic part of
the circuit, the same direction as the direct currents succeeding,
although they had momentarily brought about opposite polarities in the
electrodes.
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