130 The Bed of the Ocean. 



certain conditions, large submarine plateaux may be formed 

 in connection with the land ; their rate of accumulation will be 

 comparatively rapid, and they will have a tendency to alter the 

 configuration of the basin as well as the direction of its 

 currents. 



The lighter and finer particles are carried to a greater 

 distance from the margin, and deposited in the more central 

 parts of the basin. Their rate of accumulation will be much 

 slower ; so that an oceanic as well as an inland basin has a 

 tendency to fill up from the margin towards the centre, and 

 may end in being completely filled up, unless this gradual 

 accumulation is kept in check through the action of currents 

 which remove a portion of the deposits and transfer it elsewhere. 

 This transference is the general rule, for as the bed of a current 

 becomes more and more restricted, its velocity increases in the 

 same proportion, and with it its power to remove part of the 

 deposits. The distance to which the lighter and finer particles 

 are carried by oceanic currents before they arrive at their final 

 resting-place may amount to several thousand miles, and this 

 is probably the cause of the remarkable uniformity which has been 

 observed in the character and composition of the deposits formed 

 not only over vast areas of the same basin, but also in the 

 different oceanic basins, as compared with the variety which 

 exists in the composition of marginal deposits. 



Hence we may infer that a stratum of a nearly uniform 

 character, which is found to extend over wide areas, must have 

 been deposited at the bottom and towards the centre of an 

 oceanic basin ; while strata of lesser extent, and offering a greater 

 variety in their composition, must have been marginal deposits. 



Formation of Central Oceanic Plateaux. — The lighter 

 and finer particles distributed by oceanic currents may be 

 divided, according to their origin, into inorganic and organic 

 particles. The former are, as a rule, much heavier in comparison 



