The Probert Encyclopaedia of Ships

BOATSWAIN

On board a ship, the boatswain (pronnounced 'bo-san') was the warrant-officer in charge of the boats, sails, rigging, anchors, cordage, cables and colours. His office was also to summon the crew to their duty, to relieve the watch, etc. In the merchant navy service the boatswain was one of the crew who had charge of the rigging and oversaw the men.
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