Figure 12. Hydra sounder, made by Mr. Gibbs and colleagues on the HMS HYDRA
during the 1868 Indian Ocean expedition commanded by Captain Peter F. Shortland.
Some of the first deep soundings in the South Atlantic and Indian Oceans were
made with this instrument rigged for use with a Hodge accumulator. Among the
important soundings was one of over 3400 meters at 31.05 S Lat and 12.25E Long.