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Glossary
233
freezing which uses theevaporation of a liqueed gas to cool the sea.
water to the freezing point—see pageqg
"
GILL NET: shing net which traps pelagic sh when they endeavourto
swim through its meshes. Fish which are too large to pass through the
mesh become entangled by their gill.covers when they try to back out
from the net—see page 35
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GROUND EFFECT: principle used by the hovercraft and similar ground
effect machines. If a stream of air is directed through a hole in a at
metal plate down on to a surface, itcreates an upward thrust which
lifts the plate—see page 195
GUYOT: a at—topped submarine mountain
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HARMÇNIÇPRËDIÇTIONZ‘ methOd of
tides and tidal currents by
combining,
meehanically or _electronically, constituent wave
fbrms into a single tidal
__I40.
…
HOOKAH: any diving apparatus which receiveS breathing gas via a hose
‘
from a separate independent supply,
_
HYDROFOIL CRAF‘I‘: travels on“
projections
in the
water which_‘r‘educe the area of boat ineontact with it, The rçdùéed
‘
drag enableshydrofoil‘craft to attain higher ‘speeds tlianjcOnvenonal
displacement vessels—see page193
_
'
,
'
.
‘
HYDROGRAPHY; science which deals with the measurement and mapping
of the physical features of the seas ad océans
‘
INERTIAL NAVIGATION SYSÎÈKi‘Z“ once-setgiyes
side reference;
operatës by detëéting changes in ,direbüonj‘and speed
,
by c0ntinuous referenceto'aiCcéléro‘metets mounted
platform
*
provided by three
_
…
.
î
INTERNÂL wm; waves rrea‘red‘ïbrnrrrhthr eanlSfffäçè rit} thbon
dary … ryr dffr wtmSrhdffdy
‘
between "the twolayers is
than
canbelüëh@ larger fhàn: surfacewaves—SCG
‘
pag6138
_
‘
ISOBATH: depth contour
‘
‘
“
‘
a common name for the brom Seaweed fôund
rocky
Itbelongs to a gr0up, the Laminariales, which includes the
l "
Ï
”
;
:in navigation:
“crie mariæl
ai'î
_
-
"’
‘
…
‘
‘
_
additionalheat
rar—change in :state, such as
fromsolid to liquid, without an increase. in temperature. The fact that
a*
_
.