NATURE m MOTION. 37 



almost invisible particles, and how much is thus dropped 

 may be seen from the river Rhone, which is a thick, 

 muddy stream where it enters the Lake of Geneva, but 

 leaves it a clear, beautiful river. The same process has 

 actually choked up the mouths of the Rhine and the Dan- 

 ube ; and the Nile, whose sand-laden waters have literally 

 formed all Lower Egypt with its countless inhabitants 

 and large populous cities, now needs a canal, made by 

 human hands, to find a way and an outlet to the Med- 

 iterranean! Our own great river, the Mississippi, be- 

 comes, at its mouth, so slow and sluggish, that it can 

 no longer bear up its burden, the immense masses of 

 huge vegetable corpses, the giant trees from the far-off 

 regions, where its sources lie. They sink to the ground, 

 sand and mud fill the interstices up, and they form, here 

 as at the mouths of all large rivers, a peninsula of new, 

 firm land. The Ganges, operating on a still larger scale, 

 pours its gigantic masses far out into the sea : sweet 

 water being lighter than salt-water, they float for some 

 time above the dark green waves of the ocean; but, 

 soon they meet the tide and outside breakers; here they 

 drop their immense loads of sand, mud, and fertile soil, 

 and, in spite of an unusually high tide, form an island 

 more than two hundred miles long. 



The power of locomotion is, however, by no means 

 limited to the agency of water and fire alone. Much 

 more remarkable is it, that even without volcanic action 

 without visible efforts or spasmodic convulsions of our 

 mother earth whole tracts of land, thousands of square 

 miles large, should move up and down, and, thus, ma- 



