8,,. DEEP-SEA DEPOSITS. 27 



from the shore, we first meet with the variable deposits of the Httoral 

 and shallow-water zones. Banks of sand heaped up under the 

 influence of tidal currents, and wide stretches of mud in the deeper 

 and quieter regions. Here and there occur local accumulations of 

 shells and shelly debris. Near the loo-fathom line blue muds are 

 found, and as these are followed down the continental slope, they 

 merge, near its base, into Globigerina ooze — a deposit which extends 

 with wearisome monotony over immense areas. As we descend into 

 the abysses of the ocean, to depths exceeding 2,500 fathoms, the 

 globigerina ooze passes into " grey " ooze, and this again into red clay 

 — the most widely distributed of all the deep-sea deposits. 



The physical conditions at great depths are practically the same 

 from the equator to high latitudes. Seasonal changes are absent, and 

 the temperature is uniform. Notwithstanding this, there is a marked 

 variation in the character of the organic remains found in the deposits. 

 Foraminifera are larger and more varied in form in the tropical 

 regions. Coccoliths, rhabdoliths, and the remains of the pelagic 

 mollusca are entirely absent from the deposits of high northern and 

 southern latitudes. These variations with latitude are due to the 

 fact that the organisms which make up so large a portion of the 

 deposits live at the surface, where their distribution is determined 

 by the distribution of temperature. 



J. J. H. Teall. 



