RECORDS LEFT BY THE SEA 



may be carried out to sea for three hundred miles or more 

 before they settle. Within this three-hundred-mile zone 

 the land-derived materials are distributed over the floor 

 in orderly succession. Nearer the land we shall find 

 coarse gravel and sand. Beyond there will be tracts of 

 finer sand and silt, with patches of gravel here and there. 

 Still farther off will come fine blue and green muds, which 

 are made of the tiny particles of such materials as form 

 the ordinary rocks of the land. -But when we are once 

 past this zone of land material we come upon deposits 

 which are the ocean's own freehold materials which it 

 does not derive from the continents, but which may be 

 called oceanic in origin. First there are vast sheets of 

 exceedingly fine red and brown clay. Whence comes it ? 

 It is by far the most common deposit in all the deeper 

 parts of the ocean. It may either be the dust of volcanic 

 fragments washed away from volcanic islands, or (which 

 is much more likely) it may be supplied by eruptions 

 under the sea. For it must be remembered that the sea 

 floor is two to five miles nearer the hot rocks that are in 

 the interior of the earth than the land surface is, and 

 that consequently the water coming into contact with 

 them may cause explosions arising from the action of 

 steam. This is a question we shall have to consider later, 

 and for the present we must ask the reader to accept the 

 fact and read on. 



There is one very curious thing about this red clay, and 

 it is that the accumulations of it appear to be built 

 up very slowly. Where it occurs farthest from land 

 great numbers of sharks'* teeth with ear bones and other 



61 



