Log, Sounding Lead and Brochure

Entry

Two elongated tetrahedral buoys, a length of rope and a lead (NG-MC-1345-A, NG-MC-1345-B, NG-MC-1345-C and NG-MC-1345-D), constituting the log and sounding lead as invented by Adolphe Pécoul. The large buoy (A), serving as a sounding lead, has a wheel and spring at the top, through which a rope can be led in one way only. The rope is weighted by the lead, and as soon as the weight ceases to pull, the spring jams the rope. The smaller buoy (B), serving as a log, has an eye at the top, and two eyes on one of the sides near the base to which a rope tag with a wooden peg is attached. The end of the rope has a small wooden cylinder tied to it, in which the peg fits. The lead (C) is hexagonal with a hollow base and a hole at the top. The brochure (D) of 19 pages and 1 plate explains the operation of the apparatus and contains favourable reports on the use of the invention.

Adolphe Pécoul’s invention as described in the brochure worked with only one buoy, alternately used as sounding lead or log. Used as a log, the buoy is weighted with the lead at a fixed length of rope, the tag with the peg is attached to the rope in such a way that the buoy lies still in the water with the long end pointing downwards (weighted with the lead) and offering a flat side to the ship’s direction. As soon as the rope tightens, the tag will let go. As with an ordinary log the amount of rope veered out in a certain lapse of time determines the speed of the vessel. The use of the lead makes it less sensitive to currents. Pécoul obtained numerous medals for his invention which he lists in his brochure, amongst which one from the Académie des Arts et des Métiers in Paris, and one from the Exhibition Universelle in Paris in 1855.