DICTIONARY OF

Propeller Post 264 Proxima Centauri
Propeller Post. That part of stem framing that carries after end of stern tube, and supports
end of tail shaft.
Proper Motion. The actual movement of a heavenly body as distinguished from a
parallactic change in its position due to Earth's movement in space. Name is given, also, to
Sun's apparent movement in Ecliptic, to distinguish it from his apparent diurnal motion. 2.
The movement on a true-motion radar display of the echo of another ship. It shows her
course and speed. ('Course Steered and Speed.')
Proper Pilotage. That branch of navigation dealing with the conducting of a ship by
methods involving astronomical observations and calculations. Now termed 'Navigation' or
'Astronomical Navigation'. In Elizabethan times it meant ocean navigation.
Proper Return Port. Port to which a seaman can claim to be returned on completion of his
service to a ship.
Propogation. Movement of crest of a progressive wave.
Proportional Lengths. Relative dimensions of a ship and appropriate lengths of masts and
spars. These used to be tabulated thus:- Length of Ship = Breadth x 7. Main Yard=2.3
Breadth. Depth of Hold=LengthxO-09. Lower Topsail Yard ==1.85 Breadth. Mainmast =
Breadth x 2.25. Spanker Gaff== Breadth. Foremast=Breadthx2-09. Bowsprit=0-7 Breadth.
Mizen Mast-= Breadth x 2.
Proportional Logarithms. Used when 'Clearing a Lunar Distance'. Was the logarithm of
10,800 (the number of seconds in 3 hours) diminished by the number of seconds by which a
quantity dealt with was less than 3 hours. Proportional log. of 2 hours would be log. of
10,800 minus log. of 3600. Now quite obsolete for this purpose.
Propulsion. The driving forward of a vessel.
Protection and Indemnity Association. Association of shipowners who combine to
indemnify any of their members against third party claims and against risks not normally
covered by marine insurance.
Protest. Statement under oath, made before a notary public, concerning an actual or
anticipated loss, damage or hindrance in the carrying out of a marine adventure.
Proved. Said of anchors and chain cables when they have been tested and found to be of
required quality and strength.
Proving Establishment. Establishment where anchors and chain cables are tested and
proved. Those in Great Britain are controlled by Department of Trade and Industry.
Prow. Old name for stem of a vessel, or for the bows. 2. Alternative name for 'Proa'.
Proxima Centauri. Name given to a Centauri on account of it being the nearest star to
Earth.