36 THE WORLD BENEATH THE WAVES 



everywhere ; yet everywhere except in the solitudes 

 of the ocean it is lost amid other grosser matter, and 

 it is only in the remote abysses of the ocean that it 

 falls unmixed with other material, and in the fulness 

 of time aids in forming a deposit of appreciable 

 thickness.* 



The question will at once occur, How can such a 

 pure deposit of volcanic (and cosmic) origin ever be 

 formed ? We can understand that the sediment 

 brought down by the rivers must gradually subside 



* The main aim of this sketch is to give a clear idea of the 

 manner of formation of the chief deposits that are accumulating 

 on the bed of the ocean, and not to describe in any detail the 

 composition of the deposits themselves. It must, however, be 

 mentioned that, according to its discoverers, a large part of the 

 red clay results from the disintegration of floating pumice {i.e. 

 volcanic material carried by water, not by air). It must also be 

 mentioned that the red clay is peculiarly rich in such resistent 

 animal remains as sharks' teeth and ear-bones of whales, and 

 this, not because animal remains sink in any particular abundance 

 in the remote regions where red clay is in process of formation, 

 but because, owing to the paucity of the material that goes to 

 form red clay, the animal-remains that do fall there are much 

 more slowly entombed than they are elsewhere. Another 

 important fact that must be mentioned is, that metallic concre- 

 tions — e.g. manganese nodules — are particularly abundant in the 

 deposits from great depths, these being the result of the slow 

 chemical decompositions and recompositions that take place under 

 the peculiar abyssal conditions. Finally, it need hardly be 

 explained that the various oceanic deposits are seldom perfectly 

 pure, and that they are not separated from one another by hard 

 and fast boundary lines, but that, like most other things in 

 Nature, they grade into one another. Even in red clay, such 

 parts of the other organic oozes as are not soluble will be 

 found. 



