OCEAN DEPOSITS: RADIOLARIAN OOZE 33 



gradually become grey as the showers of shells began 

 to prevail over the gradually-diminishing showers of 

 river-borne silt, until, before we were 300 miles away 

 from land, we should be on pure Globigerina-ooze, 

 mixed only with the remains of other sea-animals, and 

 perhaps with pieces of water-logged pumice-drift. We 

 should continue on Globigerina-ooze until we came 

 within 100 miles of the west coast of the Andaman 

 Islands, where we should almost certainly see some 

 patches of Pteropod-ooze ; and, further on, we should 

 find ourselves on a tenacious whitish clay, not unlike 

 Globigerina-ooze in colour and chemical composition, 

 but differing from it in consisting almost entirely of 

 the finely-comminuted d^brh of the coral-reefs that 

 fringe the islands. 



We must, therefore, go outside the comparatively 

 narrow limits of the Bay of Bengal, whose greatest 

 depths do not much exceed 2000 fathoms, if we 

 would make our idea of the ocean floor more 

 complete. 



And first, we must take note of the fact that the 

 surface waters of the ocean support multitudes of 

 microscopic animalcules, nearly related to the Fora- 

 minifera, but differing from the latter in having shells 

 of silica, or what we may without any serious mis- 

 representation call flint. These hard-shelled animal- 

 cules are called Radiolaria, and although they are not 



nearly so abundant as the comparatively soft-shelled 



c 



