i] THE CATEGORIES OF LIFE 11 



the solvent action of the sea water. This ooze is 

 not the only one which is composed of siliceous ma- 

 terial, for in the Antarctic there is an area of ten 

 and a half millions of square miles covered with the 

 remains of diatoms. These organisms live in the 

 superficial layers of the sea in such enormous numbers 

 that their dead shells form the major part of the mud 

 covering the floor of the Antarctic. 



In the greatest depths of all, 3500 fathoms and 

 over, we find no longer any obvious indications of 

 organic structures in the mud on the sea-bottom. 

 The deposit in these great depths is called the Red 

 Clay, and it is a very soft brown mud consisting of 

 exceedingly fine particles, which are the insoluble 

 remains of the shells of pelagic plants and animals, 

 and volcanic dust settling down from suspension in 

 the water, or from the atmosphere. Among it we 

 find cosmic dust that which has originated in the 

 combustion of meteorites entering the atmosphere 

 of the earth from outer space. It accumulates with 

 exceeding slowness, for we ought to find meteoritic 

 dust in every part of the sea-bottom, but it can 

 usually be recognised only among the red clay, for 

 everywhere else it is hidden by the more abundant 

 materials. In the red clay we also find the earbones 

 of whales and the teeth of sharks. All the rest of 

 the skeletons of these great creatures have been 

 dissolved by the action of the sea water. 



