DICTIONARY OF

Bore 51 Bourdon Gauge
Bore. Steep tidal wave that develops in certain rivers and passes up in advance of normal
tide undulation. Caused by narrowing of channel and decrease in depth. Occurs in Severn,
Seine, Trent, Ganges and other rivers.
Boreas. Greek name for North wind.
Boring. Forcing a vessel through newly-formed ice.
Borrowing. Setting a course that may appear to be unsafe but will be safe through action of
wind and/or current.
Bos'n. Boatswain.
Bosom Piece. Short length of angle iron inside a butted joint of angle iron. Usually extends
for at least three rivets spaces on either side of butt.
Boson.* Old spelling of 'Boatswain'.
Boss (Propeller). That part in which blades are fixed, and through which the end of shaft
passes.
Better. Dutch coasting craft with one mast, jib and staysail and a mainsail with short gaff.
Usually double ended and with lee boards.
Bottle Screw. Left hand and right hand threaded screws led into outer ends of a shroud or
'bottle'. Has largely superseded dead-eyes and lanyards for setting up rigging.
Bottom. Name sometimes given to hull of a ship.
Bottom Boards. Light boards fitted in bottom of boat to keep all weights off bottom
planking, and on frames and timbers. Keep crew's feet dry if any water in boat.
Bottom End Bearing. Crank pin bearing, over which connecting rod of reciprocating engine
is fitted.
Bottom Plating. That part of a ship's shell plating lying between the bilge and the keel plate.
Bottomry. Pledging a ship or the freight she earns to raise money necessary to complete
voyage. Repayment is contingent on safe arrival of vessel. Name was given, originally, to
'Marine Insurance'.
Bottomry Bond. Legal document given to one who advanced money on bottomry.
Guarantees repayment on safe arrival at destination.
Bouguer's Log. Invented by French scientist in 1747. Log ship consisted of a wood cone
with a ballasting weight on a 50-ft. line, to prevent wind effect on cone.
Boulene.* Old spelling of 'Bowline'.
Boulter. Fishing line consisting of long pieces of tarred rope fitted with hooks at fathom
intervals, and sinkers near each hook.
Bound. Proceeding in a specified direction, or to a specified place.
Bourdon Gauge. Instrument for measuring pressure of steam by means of a curved piece of
flattened bronze tubing, the end of which is sealed. When steam is admitted at open end the
tube tends to straighten, thus moving sealed end. Appropriate gearing causes amount of
movement to indicate corresponding pressure.