PHYSICAL CONDITIONS OF THE DEEP SEA. 469 



ly flowing water, for if tliey did so they would soon be smothered 

 by the fine mud that composes the floor of all the deep seas. In 

 fact, anemones of the type presented by such forms as Sicyonis 

 crassa are only fitted for existence in sluggish or still water. 



Another character that must be taken into consideration is 

 that presented by the floor of the great oceans. The floor of the 

 ocean, if it were laid bare, would probably present a vast undu- 

 lating plain of fine mud. Not a rock, not even a stone, would be 

 visible for miles. The mud varies in difi^erent jmrts of the globe 

 according to the depth, the proximity to land, the presence of 

 neighboring volcanoes, or the mouths of great rivers. 



The globigerina ooze is perhaps the best known of all the dif- 

 ferent deep-sea deposits. It was discovered and first described by 

 the officers of the American Coast Survey in 1853. It is found in 

 great abundance in the Atlantic Ocean in regions shallower than 



Fici. 3. Globigekina Ooze. (After Agassiz.) 



2,200 fathoms. Deeper than this it gradually merges into the 

 " red mud." It is mainly composed of the shells of f oraminif era, 

 and of these the dift'erent species of globigerina are the most abun- 

 dant. It is probably formed partly by the shells of the dead fo- 

 raminifera that actually live on the bottom of the ocean and partly 

 by the shells of those that live near the surface or in intermedi- 

 ate depths and fall to the bottom when their lives are done. So 

 abundant are the shells of these protozoa that nearly ninety-five 

 per cent of the globigerina ooze is composed of carbonate of lime. 

 The remaining five per cent, is composed of sulphate and phos- 

 phate of lime, carbonate of ammonia, the oxides of iron and man- 

 ganese, and argillaceous matters. The oxides of iron and man- 

 ganese are probably of meteoric origin ; the argillaceous matter 

 may be due to the trituration of lumps of pumice stone and to the 

 deposits caused by dust storms. 



Globigerina ooze may be found on the floor of the ocean at 



