SUBMARINE DEPOSITS. 269 



187), and the like, as have not been removed in solution ; only 

 the densest bones remaining, around which have formed de- 

 posits of manganese (Fig. 188) and iron. Here the rate of 

 deposition is at the minimum. After this come radiolarian 

 ooze, diatom ooze, globigerina ooze, 

 and pteropod ooze, the terrige- 

 nous dejDOsits upon the shores of 

 the continents accumulating at the 

 highest rate. 



Near the shore, in proximity with 

 the hundred - fathom line, there is 

 undoubtedly held in suspension in 

 the water an immense amount of 

 decaying organic matter, both ani- 

 mal and vegetable, in connection Fig. ISS. —Section of manganese 



with the detritus swept into deeper ""d^Je showing tympanic w of Me- 



^ ^ soplodon. (Chall.) 2.600 fathoms. 



water from the shores of the con- 

 tinental masses ; and this probably accounts for the presence 

 of glauconite and phosphatic nodules in these areas. At a 

 distance from shore, the supj^ly is limited to the dead or- 

 ganic matter which finds its way to the bottom, — the re- 

 mains of the pelagic fauna and flora. In areas not in the 

 track of oceanic currents, or which do not underlie regions where 

 pelagic algse float with more or less regularity, this supply must 

 be infinitesimal. 



We owe to Pourtales the first general sketch of the bottom 

 deposits around the eastern shores of the United States. He 

 availed himself of the earlier results obtained by Professor 

 Bailey fi-om the examination of the deep-sea soundings sub- 

 mitted to him by the Coast Survey, and, supplementing these 

 by his own observatiens, he published in Petermann's Journal a 

 map of the bottom o£ the western Atlantic, adjoining the coast 

 of the United States. In that memoir he calls attention to the 

 main subdivisions of siliceous sand and calcareous de230sits, the 

 first extending along the eastern coast from New England as 

 far south as Cape Florida, and the second around the southern 

 extremity of Florida, the Bahamas, and a part of the coast of 

 Cuba. 



