Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

Copyright. THE DEPTH RECORDER. The Depth-Recorder is shown at N. As the sinker descends, the increased pressure forces the piston D up into the tube, while the spiral spring pulls the piston back. The #_A amount that the piston is forced up against the action of the spiral spring depends on the -□ depth. To record the depth the marker C is used. As the Recorder goes down, the marker is pushed along the piston. When the Recorder is brought up to the surface of the water, the piston comes back to its original position, but the marker remains at the place on the scale to which it was pushed, and shows the depth to which the Recorder has been. The depth is I read off by the marker. f CHEMICAL TUBES. When Chemical Tubes are being used instead of the Depth Recorder, one of the brass ■ guard tubes is lashed to the rope between the wire and the sinker, about 3 feet from the end EJ of the wire. Before taking a cast the officer, or leading hand, places a glass tube, with the ■ open end down, in the guard tube, and puts the cap on. When the guard tube is brought on i c board, care should be taken to keep it right side up. If it is turned on its side, or upside K down, the water will run up the glass tube and produce a bad mark. The officer takes out | | the glass tube, and applies it to the scale with the closed end against the brass plate at the gl° top of the scale. He reads off the number of fathoms shown on the scale by the lowest part ■ I of the red coating. This, without correction, will be the depth accurately enough if the i!|| barometer be at anything from 28t to 29I inches. : If; aSE- tlie Barometer stands at 29! add one fathom in 40. Photo N. >) JJ ;j ,, 30 ,, ,, 3) 30. Depth 35 11 )> 3°2 n >> ,, 20. ReCOrder- ” ” „ „ 31 „ „ „ 15. TO ASCERTAIN THE NATURE OF THE SEA BOTTOM. When it is desired to ascertain the nature of the sea bottom, hard soap makes the best arming. It should be squeezed and worked up in the hands before using. If the cavity in the bottom of the sinker has smooth sides they should be roughened with a cold chisel to retain the arming when the vessel is steaming fast, otherwise it will be washed out. 122