DICTIONARY OF

Mate's Log 220 Mean Solar Day
Mate's Log. Book kept by Mate, and recording work done by crew and, with particular
emphasis, all matters concerning stowage, carriage, ventilation and discharge of cargo.
Mate's Receipt. Document signed by Mate when goods for carriage are received into ship's
charge.
Matthew Walker. Knot put in end of rope. Made by unlaying end of rope, making a bight
of one strand, passing second strand over bight of first, passing third over bight of second
and through bight of first.
Matting Sword. Length of thin wood used for beating in the wheft of a woven, or 'sword',
mat.
Maul. Heavy hammer of iron or wood.
Mayday. (French 'm' aidez', 'Help me'.) The international spoken radiotelephony signal of
distress.
Maximum Altitude. Greatest angular distance above horizon.
Maxwell's Rule. 'Corkscrew Rule.'
McIntyre System. Double-bottom construction involving the cutting of frames and reverse
frames and the fitting of a continuous water-tight angle bar to take lower edge of tank
margin plate.
McIntyre Tank. Water-ballast tank seated on top of ordinary floors. Preceded doublebottom
tank.
Meade Great Circle Diagram. Graticule for solving great circle sailing problems from
projection of course on a Mercator chart.
Mean Draught. Half sum of forward and after draughts of a vessel. It differs slightly from
draught at half length.
Mean High Water. Mean of all high waters at a place when observed during a lunation of
29 days.
Mean High -Water Springs. Mean height of spring high waters at a place when deduced
from an adequate number of observations.
Mean Latitude. That latitude whose numerical value is half the sum of a latitude left and a
latitude reached.
Mean Low Water. Mean of all low waters at a place when observed during a lunation of 29
days.
Mean Low-Water Springs. Mean height of spring low waters at a place when deduced
from an adequate number of observations.
Mean Noon. Instant in which Mean Sun is on meridian of a place.
Mean Place of Star. That position on the celestial concave at which a star would appear to
be if viewed from Sun. It is expressed in declination north or south of Equinoctial and
sidereal time angle from First Point of Aries on January 1 of current year.
Mean Sea Level. Level that sea would maintain if no tidal effect were manifested and
average meteorological conditions prevailed. For hydrographic and surveying purposes the
level is derived from very prolonged and careful observations at an appropriate position -
Newlyn, Cornwall, being selected for British standard level.
Mean Solar Day. Interval between successive transits of Mean Sun across a given meridian.
Its length is the mean length of all apparent solar days in a year.