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FOUNDERS OF OCEANOGRAPHY 



condition at depths of 1,200 to 2,200 fathoms. At lesser 

 depths it may graduate into Pteropod ooze or coral deposits, 

 and at greater depths it gradually loses the calcareous shells 

 and passes into Red Clay at about 2,500 to 3,000 fathoms. 

 During the " Challenger " expedition, Murray calculated, 



Fig. 10. — Sketch of living Globigerina from the surface of the Atlantic 

 as seen under the microscope in plankton fresh from the tow-net. The 

 opaque protoplasm inside the shell is of a brick-red colour. The wisps of 

 spines are not seen on the shells in the ooze. 



from his tow-net observations, that one square mile of 

 tropical water 100 fathoms deep contained about 16 tons 

 of carbonate of lime in the shells of Globigerina and allied 

 organisms. These reach the bottom in a more or less perfect 

 condition, according to the depth of water through which 

 they have to fall. Once on the bottom and covered by 

 others, they are safe from further solution, and typical 

 Globigerina ooze is supposed (from the observations obtained 



