DICTIONARY OF

Babcock Erith Stoker 30 Backstaff
Babcock Erith Stoker. Mechanical apparatus for feeding boiler furnaces with coal, and so
arranging it that efficient consumption and clean fires are maintained.
Babcock Johnson Boiler. Water tube boiler of fairly small dimensions and weight, but
having very high efficiency.
Babcock Wilcox Boiler. Water tube boiler for main steam purposes. Working pressure up
to 1400 Ib. per sq. in.
Bac. Flat-bottomed boat, often with pram bow, used as a ferry.
Back. To back engines is to put them astern. To back an oar is to reverse the action of
rowing and propel the boat astern. To back a sail is to haul its clew to windward. To back
anchor is to lay another anchor ahead of it, and with a cable or hawser extending tautly
between them. Wind is said to 'back' when it changes direction anti-clockwise.
Back Altitude. Measurement of greater arc of vertical circle passing through an observed
body. Taken when horizon at foot of smaller arc cannot be distinguished.
Back and Fill. To fill sails and then back them, alternately. Done to keep vessel in a
position for the time being.
Backboard. Board athwart after end of stern sheets of a rowing boat, for passengers to lean
against.
Backbone. Fore and aft wire along middle of an awning.
Back Freight. Money payable to ship for carrying cargo back to port of shipment when it
was impossible to discharge cargo at destination.
Back Letter. Name sometimes given to a 'Letter of indemnity'.
Back Pressure. In a steam cylinder, is pressure set up by steam on exhaust side of piston.
In a pump, is resistance generated when discharge has to be forced.
Backrail. Name formerly given to 'Backboard'.
Back Rope. Small chain, or rope pendant, used for staying a dolphin striker.
Back Sailing. Hauling boom of mainsail, or mizen, to windward when a vessel loses way
in going about. This forces her head on a new tack, and is a kind of box hauling.
Back Ship. To work ship astern with sails or engines.
Back Sight. Back altitude.
Backsplice. Method of finishing off end of a rope that is not required to reeve through a
block. End is unlaid, 'crown' formed with the strands, ends tucked into rope below crown.
Backspring. Rope led aft, from forward in a ship, to a buoy, or bollard outside ship. Used
for heaving ship astern, or for preventing her ranging ahead.
Backstaff. Forerunner of quadrant and sextant. Instrument devised by Captain Davis
about 1590. Observer stood with his back to Sun and measured altitude by two concentric
rings, one measuring 30°, the other 60°.