200 THE OCEAN 



1. Terrigenous Deposits . These are mainly 

 made up of detrital materials carried down 

 from the land-surfaces or torn away from the 

 coast-line and shallow water, together with 

 the remains of organisms which live on the 

 bottom in shallow water ; quartz particles 

 are highly characteristic of these deposits. 



2. Pelagic Deposits. These are largely made 

 up of the remains of calcareous and siliceous 

 organisms which have lived in the surface 

 waters of the ocean and have fallen to the 

 bottom after death, and of an inorganic residue 

 mostly composed of hydrous silicates of iron 

 and alumina, derived chiefly from the disin- 

 tegration of pumice and other volcanic frag- 

 ments ; particles of quartz-sand are rare, if 

 not quite absent, except in regions affected 

 by floating ice. 



This scheme of classification is exhibited 

 in the table on page 201, and the accom- 

 panying map (Plate XI.) shows the general 

 distribution of the deposits over the floor of 

 the ocean. 



Other classifications have been suggested, 

 but none of them appears to be an improve- 

 ment upon, or to add to the clearness of, the 

 one here adopted. 



The littoral deposits found between tide- 

 marks and the shallow-water deposits found 

 between low- water mark and the 100-fathoms 



