482
Sea Sounding.
[Jour. Frank. Inst.
Sea S o u n d i n g . - - S i r William Thomson has recently patented an ingenious method of sounding, which can be put in practice without reducing a ship's speed. By the wire-sounding apparatus of the same inventor, a great deal of time is saved, owing to the small amount of friction of the sea water on the wire in sinking at~d in hauling in, as compared with the friction on the rough hemp surface of the leadline. Owing to the speedy execution of a wire sounding, it was also possible in shallow water to take a series of flying soundings from a ship without slackening her speed as she approached the coast-a great advantage to a mail steamer in thick weather. The new invention of Sir William Thomson measures the depth independently of the wire paid out, which, however, may serve as a check on the other result. The pressure of the sea water at the depth to which the lead sinks, is made the means of registering the depth, in the following way. A glass tube, closed at one end and open at the other, is lined inside with a coloring matter, such as aniline blue, red prussiate of potash, or, better still, chromate of silver, which will be acted upon chemically, and discolored by sea water. This tube, suitably guarded in a brass guard-tube against accidents, is lowered with the lead-line into the sea. The sea water, forcing its way into the tube by the open end, compresses the aircolumn therein, and mounts up the tube to a height corresponding to the pressure, and discolors the lining of the tube in its passage. The discoloration in the tube marks the height to which the sea water has penetrated, and this becomes a measure of the water pressure, and consequently, by employing a suitable scale, of the depth in fathoms to which the lead was sunk. A chromate of silver lining of the tube is turned from orange yellow to white, by the action of the sea water. Instead of discoloring the lining by sea water alone, the sea water itself may be tinctured by a dye as it enters the tube; or it can be arranged by proper valves simply to trap the water in the tube, and retain it there until it can be brought to the surface and its height read off. The indicator tube and leadline are used in conjunction with the pianoforte-wire apparatus. Recent trials of this new apparatus on board H. M. S. Minotaur, have proved highly satisfactory.--The Telegraphic Journal.