irect
from the machine, was sent through the galvanometer for twenty-five beats,
then interrupted for other twenty-five beats, renewed for twenty-five beats
more, again interrupted for an equal time, and so on continually. The
needle soon began to vibrate visibly, and after several alternations of
this kind, the vibration increased to 40 deg. or more.

303. On changing the direction of the current through the galvanometer, the
direction of the deflection of the needle was also changed. In all cases
the motion of the needle was in direction the same as that caused either by
the use of the electric battery or a voltaic trough (300).

304. I now rejected the wet string, and substituted a copper wire, so that
the electricity of the machine passed at once into wires communicating
directly with the discharging train, the galvanometer coil being one of the
wires used for the discharge. The effects were exactly those obtained above
(302).

305. Instead of passing the electricity through the system, by bringing the
discharging rod at the end of it into contact with the conductor, four
points were fixed on to the rod; when the current was to pass, they were
held about twelve inches from the conductor, and when it was not to pass,
they were turned away. Then operating as before (302.), except with this
variation, the needle was soon powerfully deflected, and in perfect
consistency with the former results. Points afforded the means by which
Colladon, in all cases, made his discharges.

306. Finally, I passed the electricity first through an exhausted receiver,
so as to make it there resemble the aurora borealis, and then through the
galvanometer to the earth; and it was found still effective in deflecting
the needle, and apparently with the same force as before.

307. From all these experiments, it appears that a current of common
electricity, whether transmitted through water or metal, or rarefied air,
or by means of points in common air, is still able to deflect the needle;
the only requisite being, apparently, to allow time for its action: that it
is, in fact, just as magnetic in every respect as a voltaic current, and
that in this character therefore no distinction exists.

308. Imperfect conductors, as water, brine, acids, &c. &c. will be found
far more convenient for exhibiting these effects than other modes of
discharge, as by points or balls; for the former convert at once the charge
of a powerful battery into a feeble