330 



ON THE BED OF THE 



have wonderful examples of great masses of land 

 formed by madrepores and extensive coral banks, 

 which in time assume all the characteristic features 

 of islands. These occupy considerable portions of 

 the watery bed of the ocean, and displace corre- 

 sponding portions of the fluid. Immense quanti- 

 ties of mud are also said to be deposited in the 

 Yellow Sea of China, in the great deltas formed 

 at the mouths of the Ganges, the Plate, the Ama- 

 zons, the Missisippi, the St Lawrence, the Nile, 

 the Rhine, and other large rivers, whose joint ope- 

 ration both at the surface and bottom of the ocean, 

 are continually carrying forward the same great 

 process of displacing the waters of the ocean ; for 

 it matters not to this question whether the debris 

 of the higher country which are carried down by the 

 rains and rivers, or are occasioned by tbe direct waste 

 produced by the ocean itself on the margin of the 

 land, be deposited at the bottom or surface of the 

 ocean ; they must still be allowed to displace an equal 

 or greater bulk of the fluid, and have therefore a 

 direct tendency to produce the derangement which 

 we are here endeavouring to describe. 



A striking illustration of this doctrine may be 

 drawn from M. Girard's able and ingenious obser- 

 vations on the delta of Egypt, made in 1799? and 

 published in the Mem. de VAcad. for 1817, in a 

 memoir Sur la Vallee (tEgypte, et sur Vexhausse- 

 ment seculaire du Sol qui la recouvre. It ap- 

 pears that the whole §oil of the " Valley of the 



