242
THE SEAS
by the temperature changes occurring in its interior after
the explosion—the cracking of the berg into pieces sounding
like a series of gun reports.
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Since the tragic sinking of the Titanic by an iceberg,
an Ice Patrol Service is on constant duty to give warning
to passing ships of the presence of the bergs and to study
their drift and movements.
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Curiously enough one of the rst signs of an approaching
iceberg is a rise in the temperature of the water.
The
surrounding sea water on bathing the ice becomes cooled
.
and hence heavier, and sinks, and more warm water ows
in to take its place.
But
the fresh water from the melting
of the exposed part of the berg pours down off its sides
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into the
Owing to its freshness it is considerably
_
ghter than the sea water and oats at the surface.
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from the ice melting below
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rises.
Fresh water beats up more readin than salt water,
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so that this lake of fresh water which surrounds theiceberg
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on all sides gains more heat from the sun than the sea water
(Fig. 47)— -
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.
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