SUBMARINE DEPOSITS. 277 



" There are off the coasts of North and South Carolina small rocky 

 banks slightly raised above the genei-al level of the sea bottom, consist- 

 ing of a calcareous material, which are probably the continuation of the 

 tertiary beds found inland along the adjoining shores. They are cov- 

 ered by corals (Oculina), gorgonians, and other invertebrates, and afford 

 better feeding-grounds for fishes than the sandy bottom. They are the 

 fishing-banks of the inhabitants. Similar banks are found off Cape 

 Fear, and, to judge from the nature of the corals and shells thrown up 

 on the beaches near Cape Hatteras and Cape Lookout, others probably 

 exist in their vicinity." 



In the strength of the current of the Gulf Stream the bottom 

 was washed nearly bare, and we found little animal life in the 

 trough of the stream. The bottom was composed of a hard 

 limestone, the edges of the sounding-cylinder coming up much 

 defaced. Off Charleston the whole width of the Gulf Stream 

 was swept clean. From Jupiter Inlet to the latitude of the 

 northern Bahamas the bottom specimens resembled more the 

 ooze of the Gulf of Mexico and the Caribbean, containing a 

 proportionally larger percentage of pteropod remains than the 

 ooze farther north, where the globigerinse increased in number. 



The rapid changes in the character of the mud in proportion 

 to the distance from shore and the depth are well shown in the 

 nature of the deposits at different levels along the short, steep 

 line which forms the northern slope of the Blake Plateau to 

 the south of Cape Hatteras. There we pass quickly from the 

 comparatively coarse shore mud to finer and finer ooze, which 

 becomes an impalpable silt in the deeper water beyond one 

 or two thousand fathoms, assuming at the same time a hghter 

 color. The gradual decrease of color of the bottom deposits 

 with an increase in depth is very evident in the soundings 



Chemical reactions show that these grains portion of this concretion by M. Klement, 



are phosphatic. They are similar to see Biill. M. C. Z., XII. No. 2. 

 the grains found in phosphatic nodules " The ' Challenger ' dredged on several 



dredged off the Cape of Good Hope and occasions, especially off the Cape of Good 



elsewhere, and identical in their physical Hope, concretionary masses like that 



and chemical properties with the phos- above described, but very much smaller, 



phatic grains in cretaceous rocks. Phosphatic nodules were always found 



"The manganese is infiltrated through in the deposits at less than l,oOO fath- 



the whole mass of the concretion. The oms, near continental shores, but never 



phosphatic grains are sometimes enclosed in the deeper deposits far removed from 



in the manganese. For an analysis of a land." 



