This last is graduated up to 10,000 meters. As every revolution of the wheel, B, corresponds to one meter, the number indicated by the counter represents the depth. Upon the axle of the winding pulley there is a break pulley, p. The brake, f, is maneuvered by a lever, L, at whose extremity there is a cord, C, which is made fast to the carriage, A. When, during the motions due to rolling, the tension of the steel wire that supports the lead diminishes or increases, the carriage slightly rises or falls, and, during these motions, acts more or less upon the brake and consequently regulates the velocity with which the wire unwinds. When the lead touches bottom, the wire, being suddenly relieved from all weight (which is sometimes as much as 70 kilos), instantly stops. [Illustration: FIG. 4.--GENERAL VIEW OF THE SOUNDING APPARATUS IN THE "TALISMAN:"] The maneuver of this apparatus may be readily understood. The apparatus and its weights are arranged in the interior of the vessel. A man bears upon the lever, L (Fig. 3), and the counter is set at zero. All being thus arranged, the man lets go of the break, and the unwinding then proceeds until the lead has touched bottom. During the operation of sounding, the boat is kept immovable by means of its engine, so that the wire shall remain as vertical as possible. The bottom being reached, the unwinding suddenly ceases, and there is nothing further to do but read the indication given by the differential counter, this giving the depth. [Illustration: FIG. 5.--APPARATUS FOR MEASURING THE LENGTH OF THE WIRE PAID OUT.] Near the winding pulley, there is a small auxiliary engine, M, which is then geared with the axle of the said pulley, and which raises the sounding apparatus that has been freed from its weight by a method that will be described further along. We have endeavored in Fig. 4 to show the aspect of the bridge at the moment when a sounding was about being made. From this engraving (made from a photograph) our readers may obtain a clear idea of the Thibaudier sounding apparatus, and understand how the wheel over which the wire runs is set in motion by the Brothergood engine.--_La Nature_. * * * * * CABLE GRAPNEL.