DICTIONARY OF

Port Clearance 259 Positive Slip
Port Clearance. Document certifying that vessel has liberty to leave a port. Issued by
appropriate authorities for the port. In British ports the authority is H.M. Customs. Name is
also given to the ship's Victualling Bill with Clearance Label pinned and sealed to it.
Port Dues. Established charges, made by a port authority, payable by vessels entering or
using the port.
Portfire. Casing containing an inflammable composition that bums slowly in all states of
weather.
Port Flange. Small guttering above a port hole or scuttle to deflect water running down
ship's side. Also called 'Rigol' or 'Eyebrow'.
Port Hole. Small aperture, usually circular, in ship's side. Used for lighting, ventilating and
other purposes.
Port Lanyard. Small length of rope or chain by which a port may be opened or closed.
Portlast. Gunwale, or upper edge of bulwarks, of a ship.
Port Marking. Distinctive mark put on cargo for one particular port when carrying cargoes
for more than one port.
Port of Refuge. Place or harbour, other than loading port or intended destination, to which a
vessel proceeds to avoid an imminent peril.
Portoise. 'Portlast.'
Portolan Charts. Hand-drawn charts of 14th century.
Portolani. Italian sailing directions of 13th and 14th centuries.
Port Policy. Contract of marine insurance covering risks that may arise while vessel is laid
up in port.
Port Riggle, Rigol. Rigol above a scuttle or port in an exposed position.
Port Sail. Old sail, used as a 'save-all', between a lighter and a ship that is loading or
discharging cargo.
Port Sanitary Authority. Body appointed to carry out statutory duties of a port authority in
regard to all matters concerning health and prevention of disease in connection with
shipping. Responsible for inspection of ships, and deratisation.
Port Sash. Window fitted into upper half of a square port.
Port Sill. One of the four short timbers lining a square port.
Port Speed. Rate of loading or discharging at a port when considered in conjunction with
the working hours of the port.
Portuguese Man of War. Jellyfish with large oblong air-bag and pendulous tentacles.
Stings when touched.
Portuguese Sennit. Alternative name for 'Boatswain's Plait'.
Position Circle. 'Circle of Position.'
Position Lights.* Two all-round white lights, vertically, shown by a warship when in
company.
Position Line. 'Line of Position.'
Positive Slip. Difference between theoretical advance of ship, by propeller action, and the
actual advance made when it is less than theoretical advance. Due to propeller working in a
yielding medium. ('Slip.')