Boats are also known by their purpose or duty; as, —
Also by specific names of various imports; as, —
Gondola, most of which are described under their respective heads.
A boat-bridge consists of a track laid on a number of boats anchored parallel in the stream, or moored to ropes or chains which pass from bank to bank.
The bridge thrown across the Hellespont by Xerxes when he invaded Greece, 480 B. C., had a length of 500 paces, and was supported on ships used as pontons. Suspension cables of flax and biblos united the ship