CHAPTER HI
‘
_
The Sea Bottom
'
BOTTOM
BEFORE we discuss the animals which inhabit the bed of
the ocean at different depths and in different zones, we
must rst say a little about the nature of the deposits
which cover the bottom, in or on which the animals live.
The study of these deposits formed the greater part of
,
life.—work of the famous Scottish oceanographer,‘ Sir john
Murray, who was one of the scientists on the Challenger
expedition.
It is to him that we are indebted for the bulk
of our knowledge on this subject, for, as a result of his
'
exhaustive study
collected on that expedition
and on later expeditions, he was able to Classify the ocean
—deposits into a series of groups which later research has .
completely conrmed.
_
Broadly speaking, there are two types of bottom deposits.
There are those formed by the settling of material washed
down from the land by rivers or worn away by wave action,
1
which
called Terrigggpus deposits and which are—
found in deep and shallow Water near the
The only
regions where this type of deposit is found any great
distance from land is opposite the months of the greatest
yers,
such as the Amazon, which brings down great
quantities of material in suspension which the strong current
'
of the river carries far out to sea.
It might be thought
that material in Suspension would not sink réadin in the
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