24 



NATURAL SCIENCE 



[July 



ventured to say that it would not be a Globigerina Ooze, founding 

 that opinion on the fact that only one or two small Foraminifera 

 had been observed in the tow-nets for several days. When a 

 white-coloured deposit was brought on board from 1260 fathoms 

 the laugh was rather against ' the philosophers,' for in external 

 appearance it greatly resembled the calcareous oozes of the Atlantic. 

 On examination, however, it was found to be a Diatom Ooze with 

 only relatively few Globigerina shells. 



The most striking peculiarity in connection with the distribution 

 of these dead shells on the floor of the ocean is the fact that they 

 are wholly absent from all the greater depths of the ocean,- although 

 at the surface their living representatives are as abundant over 

 these deep areas as elsewhere. If we suppose a volcanic cone to 

 rise from the greater depths of the ocean up to within 400 or 300 

 fathoms of the surface, it will be found that the summit of this 

 cone is covered with a calcareous deposit for the most part made up 



Fig. 5.— Globigerina Ooze, from 1900 fathoms in the Atlantic ; magnified 25 diam. 



of the dead shells of pelagic organisms, the deposit may contain 

 90 per cent, of carbonate of lime, and in it every species of shell 

 met with in the surface waters of the region is represented. As 

 we descend the sides of this cone into deeper water, the thinner 

 and more delicate shells, like Candcina and Hastigerina, disappear 

 first from the deposit (along with the Pteropod shells). In about 

 2000 fathoms the deposit consists chiefly of pelagic Foraminifera, 

 and the proportion of young shells is much smaller than in the 

 deposits at lesser depths. With increasing depth the whole of 

 these calcareous shells gradually disappear, till at 4000 and 5000 

 fathoms probably not a vestige of them can be traced, and the 

 deposit all round the cone in 3000 fathoms becomes a Red Clay 



