ECHO SOUNDER

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The apparatus consists of (1) a transmitter fitted inboard to the
bottom of the ship to produce a sound wave under water; (2) a sensitive
receiver of the echo reflected from the seabed known as the hydrophone;
(3) recording gear for measuring the interval of time between the sound
impulse and the sound echo. The transmitter and receiver are fitted
on opposite sides of the ship as indicated in Figure 6 and the recording
apparatus is placed on the bridge.

Fig. 6.—The Path of the Sound.
The method of taking soundings i& simple. The observer pulls
down the writing table in front of the instrument^ thus exposing fso
view the depth scale which he turns back till brought Lnp by tb-e stop at
the lower end of the scale. He now switches on the gear by Jbo