rection: currents therefore would exist in these moving parts,
proceeding from one pole of rotation to the other; but the currents above
would be in the reverse direction to those below, and in conjunction with
them would produce a continued circulation of electricity.

162. As the electric currents are nowhere interrupted in the ball, powerful
effects were expected, and I endeavoured to obtain them with simple
apparatus. The ball I used was of brass; it had belonged to an old
electrical machine, was hollow, thin (too thin), and four inches in
diameter; a brass wire was screwed into it, and the ball either turned in
the hand by the wire, or sometimes, to render it more steady, supported by
its wire in a notched piece of wood, and motion again given by the hand.
The ball gave no signs of magnetism when at rest.

163. A compound magnetic needle was used to detect the currents. It was
arranged thus: a sewing-needle had the head and point broken off, and was
then magnetised; being broken in halves, the two magnets thus produced were
fixed on a stem of dried grass, so as to be perpendicular to it, and about
four inches asunder; they were both in one plane, but their similar poles
in contrary directions. The grass was attached to a piece of unspun silk
about six inches long, the latter to a stick passing through a cork in the
mouth of a cylindrical jar; and thus a compound arrangement was obtained,
perfectly sheltered from the motion of the air, but little influenced by
the magnetism of the earth, and yet highly sensible to magnetic and
electric forces, when the latter were brought into the vicinity of the one
or the other needle.

164. Upon adjusting the needles to the plane of the magnetic meridian;
arranging the ball on the outside of the glass jar to the west of the
needles, and at such a height that its centre should correspond
horizontally with the upper needle, whilst its axis was in the plane of the
magnetic meridian, but perpendicular to the dip; and then rotating the
ball, the needle was immediately affected. Upon inverting the direction of
rotation, the needle was again affected, but in the opposite direction.
When the ball revolved from east over to west, the marked pole went
eastward; when the ball revolved in the opposite direction, the marked pole
went westward or towards the ball. Upon placing the ball to the east of the
needles, still the needle was deflected in the same way; i.e. when the ball
revolved from