deflections were read off through a glass
plate in the case, by means of a telescope and scale placed at a
considerable distance from the instrument.

A pair of bismuth cylinders was first examined. Sending a current
through the helices, and observing that the magnets swung perfectly
free, it was first arranged that the bismuth cylinders within the
helices had their central or neutral points opposite to the poles of
the magnets. All being at rest the number on the scale marked by the
cross wire of the telescope was 572. The cylinders were then moved,
one up the other down, so that two of their ends were brought to bear
simultaneously upon the magnetic poles: the magnet moved promptly, and
after some oscillations [Footnote: To lessen these a copper damper was
made use of.] came to rest at the number 612; thus moving from a
smaller to a larger number. The other two ends of the bars were next
brought to bear upon the magnet: a prompt deflection was the
consequence, and the final position of equilibrium was 526; the
movement being from a larger to a smaller number. We thus observe a
manifest polar action of the bismuth cylinders upon the magnet; one
pair of ends deflecting it in one direction, and the other pair
deflecting it in the opposite direction.

Substituting for the cylinders of bismuth thin cylinders of iron, of
magnetic slate, of sulphate of iron, carbonate of iron, protochloride
of iron, red ferrocyanide of potassium, and other magnetic bodies, it
was found that when the position of the magnetic cylinders was the
same as that of the cylinders of bismuth, the deflection produced by
the former was always opposed in direction to that produced by the
latter; and hence the disposition of the force in the diamagnetic body
must have been precisely antithetical to its disposition in the
magnetic ones.

But it will be urged, and indeed has been urged against this
inference, that the deflection produced by the bismuth cylinders may
be due to induced currents excited in the metal by its motion within
the helices. In reply to this objection, it may be stated, in the
first place, that the deflection is permanent, and cannot therefore be
due to induced currents, which are only of momentary duration. It has
also been urged that such experiments ought to be made with other
metals, and with better conductors than bismuth; for if due to
currents of induction, the better the conductor the more exalted will
be the effec