BYSSA. An ancient gun for discharging stones at the enemy.
BYSSUS. The silken filaments of any of the bivalved molluscs which
adhere to rocks, as the _Pinna_, _Mytilus_, &c. The silken byssus of the
great pinna, or wing-shell, is woven into dresses. In the _Chama gigas_
it will sustain 1000 lbs. Also, the woolly substance found in damp parts
of a ship.
BY THE BOARD. Over the ship's side. When a mast is carried away near the
deck it is said to go by the board.
BY THE HEAD. When a ship is deeper forward than abaft.
BY THE LEE. The situation of a vessel going free, when she has fallen
off so much as to bring the wind round her stern, and to take her sails
aback on the other side.
BY THE STERN. When the ship draws more water abaft than forward. (_See_
BY THE HEAD.)
BY THE WIND. Is when a ship sails as nearly to the direction of the wind
as possible. (_See_ FULL AND BY.) In general terms, within six points;
or the axis of the ship is 67-1/2 degrees from the direction of the
wind.
BY-WASH. The outlet of water from a dam or discharge channel.