irectly. The fractions of a meter, as well as the times, are in the
margin. Thus, at the point, a, the apparatus gives at 3 o'clock and
20 minutes a height of tide of 4.28 m. above the level of the lowest
water.

This apparatus might possibly operate well, and yet not be in accord
with the real indications of the float, so it has been judged
necessary to add to it the following control.

Every time the float reaches 3 meters above the level of the lowest
tide, the circuit of one of the lines that is open at this moment
(that of line I, for example) closes at C (Fig. 2), into this new
circuit there is interposed a considerable resistance, W, so that the
energy of the current is weakened to such a point that it in nowise
influences the normal travel of the wheel, r. At the shore station,
there is placed in deviation a galvanoscope, K, whose needle is
deflected. It suffices, then, to take datum points upon the
registering apparatus, upon the wheel, T, and the screw, a, in such
a way as to ascertain the moment at which the stylet, g, is going to
mark 3 meters. At this moment the circuit of the galvanoscope, K, is
closed, and we ascertain whether there is a deviation of the needle.

As the sea generally rises to the height of 3 meters twice a day, it
is possible to control the apparatus twice a day, and this is fully
sufficient.

It always belongs to practice to judge of an invention. Mr. Von
Hefner-Alteneck tells us that two of these apparatus have been set
up--one of them a year ago in the port of Kiel, and the other more
recently at the Isle of Wangeroog in the North Sea--and that both have
behaved excellently since the very first day of their installation. We
shall add nothing to this, since it is evidently the best eulogium
that can be accorded them.--_La Lumiere Electrique._

* * * * *

DELUNE & CO.'S SYSTEM OF LAYING UNDERGROUND CABLES.

In recent times considerable attention has been paid to the subject of
laying telegraph cables underground, and various methods have been
devised. In some cases the cables have been covered with an armor of
iron, and in others they have been inclosed in cast-iron pipes. For
telephonic service they are generally inclosed in leaden tubes. What
this external envelope shall be that is to protect the wires from
injury is a question of the highest importance, since not only the
subject of protection is concerned, but also that of cost. It is
t