CHAPTER III 

 The Sea Bottom 



Bottom Deposits 



Before we discuss the animals which inhabit the bed of 

 the ocean at different depths and in different zones, we 

 must first 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 the 

 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 of samples 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 confirmed. 



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, 

 which Murray called Terrigenous deposits and which are 

 found in deep and shallow water near the land. The only 

 regions where this type of deposit is found any great 

 distance from land is opposite the mouths of the greatest 

 rivers, 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 readily in the 



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