"When navigating in shallow water it is always necessary, even if they are well charted and one is reasonably sure of the ship's position, to keep informed as to the depth of water underneath her.
The simplest method of doing this is to use the ' hand-lead ' which has persisted unchanged for centuries. It is simply a lead plummet, weighing several pounds, to which a hemp line, marked in fathoms, is attached.
Standing in the ' chains ' - a small platform built out over the side-the leadsman swings the lead over his head and lets it fly forward, dropping into the water as far ahead as possible.
Gathering in the slack of the line until this gradually comes vertical, he notes whether the lead is on the bottom or not and how much line is out-then he calls, in a peculiar and traditional cadence, either the depth found or the fact that he has ' No bottom at - fathoms.'" — The Instruments of Navigation
