234
Glossary
the heat of fusion is lower than the heat of evaporation is one of the
main reasons for attempts to desalinate water by freezing rather than
distillation processes
LONG—LINE FISHING: use of long weighted line with side branches ending
in hooks to catch mainly demersal and midwater sh
LORAN (LONG RANGE NAVIGATION): American navigational system which
xes ship position by reference to the difference in time of synchronized
radio signals from two xed transmitters
MARIGRAM: the rise and fall of the tide plotted against time
MASCARET—see bore
MULTISTAGE FLASH DISTILLATION (MSF): desalination process in which
sea—water is fed into a succession of chambers at progressively lower
pressures. Some of the hot water ‘ashes’ to steam when entering each
chamber leaving the salt behind, because the boiling point of water
becomes lower as the pressure is reduced—see page 76
NAUTICAL MILE: length of one minute of arc along any great circle on the
surface of the Earth. Since this varies with latitude, the nautical mile is
agreed internationally to be equal to 1,852 metres (6,076-103 feet or
r-1508 statute miles)
NEAP TIDE—see tides
NEKTON: collective name for all animals which swim in the sea
NITROGEN NARCOSIS: effect on a diver’s mental processes of excess
nitrogen dissolved into his body uids and tissues. When a scuba diver
breathing normal air, which contains 80 per cent nitrogen, descends
much below 60 feet, the nitrogen begins to impair his performance.
The narcotic effects become progressively worse with increasing depth
so that by 300 feet even routine tasks become practically impossible.
For deep dives, the nitrogen is largely or completely replaced by an
inert gas, usually helium. The amount of oxygen in the breathing
mixture is also reduced since this gas, normally considered a life—
giver, becomes toxic under pressure if present in the proportions
found in air—see page 160
OTTER TRAWL—see tmwl
PELAGIC FISH: sh found in the Surface waters of the sea—see page 33
PELAGIC SEDIMENTS: deposits found on the ocean oor remote from any
land. They are generally very ne and range in colour from white to a
dark reddish—brown. Pelagic sediments containing less than about
30 per cent of organic remains are called red clay, while those contain—
ing more than this are known as oozes—see page 114
Glossary
the heat of fusion is lower than the heat of evaporation is one of the
main reasons for attempts to desalinate water by freezing rather than
distillation processes
LONG—LINE FISHING: use of long weighted line with side branches ending
in hooks to catch mainly demersal and midwater sh
LORAN (LONG RANGE NAVIGATION): American navigational system which
xes ship position by reference to the difference in time of synchronized
radio signals from two xed transmitters
MARIGRAM: the rise and fall of the tide plotted against time
MASCARET—see bore
MULTISTAGE FLASH DISTILLATION (MSF): desalination process in which
sea—water is fed into a succession of chambers at progressively lower
pressures. Some of the hot water ‘ashes’ to steam when entering each
chamber leaving the salt behind, because the boiling point of water
becomes lower as the pressure is reduced—see page 76
NAUTICAL MILE: length of one minute of arc along any great circle on the
surface of the Earth. Since this varies with latitude, the nautical mile is
agreed internationally to be equal to 1,852 metres (6,076-103 feet or
r-1508 statute miles)
NEAP TIDE—see tides
NEKTON: collective name for all animals which swim in the sea
NITROGEN NARCOSIS: effect on a diver’s mental processes of excess
nitrogen dissolved into his body uids and tissues. When a scuba diver
breathing normal air, which contains 80 per cent nitrogen, descends
much below 60 feet, the nitrogen begins to impair his performance.
The narcotic effects become progressively worse with increasing depth
so that by 300 feet even routine tasks become practically impossible.
For deep dives, the nitrogen is largely or completely replaced by an
inert gas, usually helium. The amount of oxygen in the breathing
mixture is also reduced since this gas, normally considered a life—
giver, becomes toxic under pressure if present in the proportions
found in air—see page 160
OTTER TRAWL—see tmwl
PELAGIC FISH: sh found in the Surface waters of the sea—see page 33
PELAGIC SEDIMENTS: deposits found on the ocean oor remote from any
land. They are generally very ne and range in colour from white to a
dark reddish—brown. Pelagic sediments containing less than about
30 per cent of organic remains are called red clay, while those contain—
ing more than this are known as oozes—see page 114