168
THE SEAS'
.
and thirty degrees south of the equator. In this region they
are to be found everywhere—except'on the western shores
of continents—that the necessary shallow water conditions
prevail, and the coloured patches on the map shown in Plates
63 and 64 indicate how widespread are coral reefs and islands.
The Great Barrier Reef of Australia, the greatest corail for—
mation in the world, is 1,260
long, extending from New
"
Guinea southward along the entire coast of Queensland.
Three
types of coral reefs have been distinguished
since the rst investigations by early navigators. -Fring—
ing Reef$ develop around the shores of islands or” conti.
nents and have'no
extensive or deep—water channel between
them and the land.
Barrier Reefs are also found o
land masses, but at- 'a much greater distance from them,
so that there is a wide and relatively deep channel between.
,
them and the shore, through Which Ships can safely pass. -
Finally there are Ai_ole, which are not connected with
land at all and consist of rings of coral, partly ‘raised v
above the surface of the sea
(Fig. 34).'
Within this
'
ring is invaably a lagoon, the depth of wlch.—'—like that
which separates a barrier reef from the land—seldom exceeds
thirty fathomS and is usually much less, and varies in size
between a mere pobl and an enClosed sea perhaps forty miles
'
from side to side.
'
‘
_
The formation of '
fringing and barrier reefs is clearly
.
'
bound up with the structure of the land they border, to the
constitution of which, ho'wever, they do not contribute,
although, as the result of the raising of the land in past ages,
_
dry land-in many regions is composed of coral limestone,
.
originally formed in the
now in
Caseswithin
mountains several thousands of feet aboVe the level of the
sea-: The formation of thereal ‘“coral islands ” or atolls is
not associated with land, from which they may be separated '
“
by hundreds of miles, the land formed being purely of coral
THE SEAS'
.
and thirty degrees south of the equator. In this region they
are to be found everywhere—except'on the western shores
of continents—that the necessary shallow water conditions
prevail, and the coloured patches on the map shown in Plates
63 and 64 indicate how widespread are coral reefs and islands.
The Great Barrier Reef of Australia, the greatest corail for—
mation in the world, is 1,260
long, extending from New
"
Guinea southward along the entire coast of Queensland.
Three
types of coral reefs have been distinguished
since the rst investigations by early navigators. -Fring—
ing Reef$ develop around the shores of islands or” conti.
nents and have'no
extensive or deep—water channel between
them and the land.
Barrier Reefs are also found o
land masses, but at- 'a much greater distance from them,
so that there is a wide and relatively deep channel between.
,
them and the shore, through Which Ships can safely pass. -
Finally there are Ai_ole, which are not connected with
land at all and consist of rings of coral, partly ‘raised v
above the surface of the sea
(Fig. 34).'
Within this
'
ring is invaably a lagoon, the depth of wlch.—'—like that
which separates a barrier reef from the land—seldom exceeds
thirty fathomS and is usually much less, and varies in size
between a mere pobl and an enClosed sea perhaps forty miles
'
from side to side.
'
‘
_
The formation of '
fringing and barrier reefs is clearly
.
'
bound up with the structure of the land they border, to the
constitution of which, ho'wever, they do not contribute,
although, as the result of the raising of the land in past ages,
_
dry land-in many regions is composed of coral limestone,
.
originally formed in the
now in
Caseswithin
mountains several thousands of feet aboVe the level of the
sea-: The formation of thereal ‘“coral islands ” or atolls is
not associated with land, from which they may be separated '
“
by hundreds of miles, the land formed being purely of coral