But if this were all, we could hardly descrihe water as an active 

 worker; it might he better described as a mere busybody. You will 

 be able to discover which it is if you fill a glass jar with water from 

 the nearest brook or river, and let it stand for a few hours. You 

 will find that the water becomes much clearer, and that a layer of 

 muddy matter forms at the bottom. Dip off all of the water you can 

 without disturbing the mud, and then leave the Jar in the sun until 

 the rest of the water dries ivp, and you will find that you have a crust 

 like clay at the bottom. Now, evidently, the mud did not come down 

 in the rain, for if you test some pure rainwater in the same way noth- 

 ing whatever 'will settle to the bottom. Hence, the mud must have 

 been taken from the ground over which the water passes. Thus 

 every stream carries oflE some of the materials which it meets in its 

 course. 



Now, what becomes of all the mud that the streams thus carry off? 

 iluch of it, no doubt, settles to the bottom of the river. But the 

 river itself is always taking up more from its banks. Hence it is clear 

 that the river must always be carrpng earth to its mouth where it 

 empties it into the ocean. If you examine a map of the mouth of a large 

 river, such as the Mississippi, you will observe that it has a very 

 curious form, as if the river had dragged the land out into the sea; 

 and so, in fact, it has, for it has built up banks of mud from the 

 material it has carried from far inland. Part of its burden it carries 

 still further than the banks at its mouth, bearing it even for some 

 distance out into the ocean. 



The quantity of mud thus carried out to sea by the Mississippi is 

 enormoiis. It amounts to 400,000,000 tons every year. Thus the 

 rivers are ever busy transporting the mountains into the sea. 



But is this work useful? Much of it certainly is. Those of you 

 who live near a river with very low banks will probably think of one 

 very useful form that it takes. In the springtime the river often 

 overflows the bottom lands near it and deposits on them some of the 

 soil which it has taken from elsewhere, thus greatly increasing their 

 fertility. Many rivers were formerly much larger and deeper than at 

 present and the very fertile land found along their banks was formed 

 by deposits of soil in the way mentioned. This, evidently, is very 

 useful work. 



But rivers are not content to carry off mud only. They can even 

 pick up pebbles when they are running swiftly. The gravel which 

 you find along the banks is evidence of this. In countries that are 

 more mountainous and where the streams move more swiftly, rapid 

 torrents can even carry off stones that weigh many pounds, and in some 



