58 



THE OPAL SEA 



Haunts of 

 the octopus. 



watersheds of mighty rivers. For hundreds 

 and hundreds of miles, under an average depth 

 of twelve thousand feet, stretch these basins of 

 the sea, rolling basins with rounded surfaces 

 that have no outcroppings of rock in peak or 

 precipice — mere wastes of soft mud. It is not 

 possible to imagine anything more drear than 

 these cold phosphorescent haunts of the octo- 

 pus, reaching seaward with unending monotony. 

 When closely examined under a glass the 

 make-up of the sea floor is not found to be of 

 one kind of mud alone. The dredgings of the 

 Challenger, the Blake, and other ships, reveal 

 a large variety of deposits; and these have ad- 

 mitted of some scientific classification. The 

 shallow-water deposits, as already noted, are of 

 finer gravels and sands washed down from the 

 continental shelves and carried out to sea by 

 vagrant shore currents. The nature of the 

 coast usually suggests the quality of the de- 

 posits lying off it — a granite coast with much 

 iron in it producing the typical red sands, 

 coral islands producing coral sands, and vol- 

 canic reefs casting down volcanic debris. The 

 beds of semi-enclosed waters, such as the seas 

 of China and Japan, or such vast inlets as the 

 Baltic or the Black Sea, are made up of simi- 

 lar " terrigenous deposits," as they are called. 



Make-up of 

 the sea 

 muds. 



Terriaenous 

 deposits. 



