484 THE CARRYING POAVERS OF STREAMS. 



fleets and commerce of many nations upon their broad 

 and ample bosom. 



Here the river reaches the close of its existence ; for 

 like everything else on earth, rivers live and die. They 

 run their appointed courses, and are then finally blotted 

 out of existence, and absorbed in that eternity of 

 waters called the ocean. This last stage of their exis- 

 tence may be briefly told in the figurative language 

 of the Arab storyteller, describing the close of his 

 hero's career : " They departed, and went, even unto 

 the mercy of Allah; and they became as though they 

 had never been." 



The carrying powers of water, by which great masses 

 of stone are removed for long distances, by mountain 

 torrents, are as we have said exceedingly remarkable ; 

 but the same power when exercised by an ordinary 

 river current along its plains track, is if possible still 

 more remarkable. 



Vast, and altogether apparently incredible quantities 

 of matter, are thus continually being carried by rivers 

 first from the highlands down into the plains, and 

 finally from the plains into the ocean. This matter 

 may be roughly said to consist of: (i) Boulders, or 

 water- worn pebbles of considerable size; (2) Gravel, 

 or debris of rock reduced to smaller fragments, also 

 much water- worn ; - - (3) Sand, or the same reduced to 

 powder; (4) Mud, or silt, consisting of clay and 



earthy matters, more or less held in mechanical solu- 

 tion by the water ; (5) Mineral salts or organic matters, 

 held in chemical solution, and generally for the most 

 part existing in invisible form in the water. 



The larger boulders are generally confined to those 

 portions of the river where the water runs swiftly, such 



