;^6 The Great World's Farm 



Mississippi, which becomes a dense yellow torrent after it 

 is joined by the Missouri, and brings down with it a heavy 

 load of mud, ground from mountains three thousand miles 

 away, which it has deposited in som.e places to a depth of 

 three hundred feet. 



And so again, on a smaller scale, the low plain at the 

 head of the Lake of Geneva is formed of mud from the 

 mountains, which the Rhone has brought down and de- 

 posited in the lake, adding to it year by year, until it has 

 risen above the water, and Port Vallais, which stood on 

 the margin of the lake in Roman times, now lies a mile 

 and a half inland. 



Inundations are caused usually either by excessive rain, 

 such as that which falls periodically in Abyssinia, or by 

 the mehing of the snow in spring; but passing mention 

 must here be made of certain inundations brought about 

 by very different causes, namely, the work of the beaver. 

 This animal, though it stih inhabits the north of Europe 

 and Asia, is nowhere now so plentiful as in North America, 

 where, also, the effect of its work in the past may best be 

 observed. 



But the beaver once abounded in England and Wales, 

 and indeed throughout the greater part of Europe, as the 

 names of many places, such as Beverley, Beverstone, 

 Biverbike, and many others, plainly show. What we see 

 of its work in America, therefore, is probably only a speci- 

 men of v/hat it has done wherever it has been undisturbed. 

 Here, at all events, thousands of acres of land have been 

 submerged, at one time and another, as the result of its 

 labors. As is well known, the beaver is in the habit of 

 building dams; and these are often so solid and extensive 

 as to stop up the streams and rivers in which they are 



