518 Mr. J. Murray on Oceanic Deposits examined 



long. 73° 56' W. A blue mud with a red upper layer containing : — 

 Much amorphous blue clayey matter ; many very fine mineral parti- 

 cles of quartz, mica, and a few of the green glauconitic particles ; a 

 good many Eadiolaria and Diatoms. 

 The top layers contained no carbonate-of-lime organisms. In those in 



the lower part of the tube there were a pelagic Foraminifer and Coccoliths. 



The tow-nets at the trawl each contained a little red mud without any 



pelagic Foraininifera. On the framework of the trawl were several large 



patches of blue mud. 



Eemaeks cw the fobegoing List. 

 Several kinds of deposits have been indicated in the foregoing list. For 

 the present these may be classed under the following heads : — 



1. Shore-deposits. 



(a) Blue and green muds. — Met with near the shores of most of the 



great continents and islands. 



(b) Grey muds and sands. — Met with chiefly near oceanic islands of 



volcanic origin. 



(c) Red mud. — Met with on the eastern coast of South America. 



(d) Coral-mud. — Met with near coral reefs. 



2. Globigerina-ooze. — An abundant oceanic deposit not met with south 



of latitude 50° S. 



3. Radiolarian ooze. — An oceanic deposit met with only in the Western 



and Middle Pacific. 



4. Diatomaceous ooze. — An oceanic deposit met with only south of 50° S. 



latitude. 



5. Red and Grey Clays. — The most abundant oceanic deposit. 



The above names have been selected as indicating those elements which 

 give the predominating character of the deposit. As a rule, when the 

 debris of continents or islands, the dead shells of Foraininifera, the exu- 

 via) of Eadiolarians &c, the frustules of Diatoms, or red or grey clayey 

 matter — when any of these have appeared to make up considerably more 

 than one half of the specimen under examination, it has been called a 

 shore-deposit, a Globigerina, Eadiolarian, or Diatom ooze, or red or grey 

 clay. 



Sometimes it has been doubtful whether a specimen should be placed 

 under one of the above heads or another, on account of the nearly equal 

 ratio of constituents, or where one deposit overlies another of a different 

 kind. In these cases the specimen has been placed under that head 

 with which, on a general view, it has seemed to have most in common, 

 or to which the surface-layer belonged, and a detailed description has 

 been added in the list. A sixth kind of deposit or formation might have 

 been added, to embrace those bottoms in which a great quantity of the 

 peroxide of manganese occurs. This substance, in the form of nodules 

 or concretions, of incrustations or in grains, has been found in nearly all 



