n, w, which revolves
over the toothed wheels, s1, s2, and s3. The thickness of w
is equal to that of the three wheels, s1, s2, and s3, and a
special spring secures at every instant an intimate contact between
the pinion and the said wheels. These latter are insulated from each
other and from the axle upon which they are keyed, and communicate,
each of them, with conductors, I., II., and III. They are so formed
and mounted that, in each of them, the tooth in one corresponds to the
interspace in the two others. As a result of this, in the motion of
the pinion, w, the latter is never in contact with but one of the
three wheels, s1, s2, and s3.

If we add that the lines, I., II., and III. are united at the shore
station with one of the poles of a pile whose other pole is connected
with the earth, and that w communicates with the earth through the
intermedium of R, and the body of the apparatus, it is easy to see
that in a vertical motion of the float in one direction we shall have
currents succeeding each other in the order I., II., III., I., II.,
etc., while the order will become III., II., I., III., II., etc., if
the direction of the float's motion happen to change.

[Illustration: FIG. 3.]

[Illustration: FIG. 4.]

In order to understand how a variation in currents of this kind can be
applied in general for producing a rotary motion in the two
directions, it will only be necessary to refer to Figs. 3 and 4. The
conductors, L1, L2, and L3 communicate with the bobbins of
three electromagnets, E1, E2, and E3, whose poles are bent at
right angles to the circumference of the wheel, R. There is never but
one pole opposite a tooth. The distance between two consecutive poles
must be equal to a multiple of the pitch increased (Fig. 3) or
diminished (Fig. 4) by one-third thereof. It will be seen upon a
simple inspection of the figures that R will revolve in the direction
of the hands of a watch when the currents follow the order L1,
L2, L3, etc., in the case shown in Fig. 3, while in the case
shown in Fig. 4 the rotary motion will be in the contrary direction
for this same order of currents. But, in both cases, and this is the
important point, the direction of rotation changes when the order in
the succession of currents; is inverted. Fig. 6 gives a perspective
view of the registering apparatus, and Fig. 5 represents it in
diagram. It will be at once seen that, the toothed wheel, r, is
reduced to its simplest expression, sin