three ordinary conductors covered with gutta percha and surrounded with a leaden sheath, which latter is itself protected against accident by means of a strong covering of iron wire and hemp.  The return is effected through the earth.  We shall enter into details concerning each of these two apparatus in-succession, by beginning with the float, of which Fig. 1 gives a general view, and Fig. 2 a diagrammatic sketch.  The float moves in a cast iron cylinder, having at its lower part a large number of apertures of small diameter, so that the motion of the waves does not perceptibly influence the level of the water in the interior of the cylinder.  It is attached to a copper ribbon, B, whose other extremity is fixed to the drum, T. The ribbon winds around the latter in the rising motion of the float, owing to a spiral spring arranged so as to act upon the drum.  The tension of this spring goes on increasing in measure as the float descends.

[Illustration:  FIG. 1.—­FLOAT OF SIEMENS AND HALSKE’S MARIGRAPH.]

[Illustration:  FIG. 2.]

This difference in tension is utilized for balancing at every instant the weight of the ribbon unwound, and thus causing the float to immerse itself in the water to a constant degree.  The ribbon, B, is provided throughout its length with equidistant apertures that exactly correspond to tappets that project from the circumference of the wheel, R. When the float moves its position, the wheel, R, begins to turn and carries along in doing so the pinion, 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.]