We thus see that a sjoring is a place where water comes to the sur- 

 face after a long underground journey. Is it the same kind of water 

 as when it went in ? Try a drink of fresh rainwater and then a drink 

 of spring or well water, and see. You will prohably find the rain- 

 water rather flat and tasteless compared with the spring water. The 

 difference mil remind you of how food, for instance oatmeal, tastes 

 with and without salt. In fact, the spring water does contain salt, 

 while the rainwater does not. There are places where springs are so 

 salt that thousands of tons of salt per year are gotten from them. 

 But the spring water contains other things also, chiefly lime, and 

 this is what is left when the water is boiled away in a kettle. Thus 

 we see that water is continually busy transporting materials from the 

 depths of the earth to the surface. The things .which are thus 

 brought up are often of great importance. The lime contained in 

 the water furnishes material for the bones of animals and the iron, 

 which is another ingredient, supplies the coloring matter for their 

 blood. It is true that most of what is needed of these materials is 

 gotten from our solid food, but as spring water contains them it is 

 healthier than rainwater for drinking and cooking. When we thus 

 think of the water carrying away material from the solid rock we can 

 see how so many cracks and fissures come to exist. As water passes 

 through a very small crack it carries some material away with it, and 

 so enlarges the crack, and so the crack grows until quite a stream can 

 pass through. 



We now see how rivers continue to run during hot weather when no 

 rain falls. They are supplied by the water from springs and under- 

 ground streamlets, and as this water often has great distances imder- 

 ground to travel it only reaches the river a long time after it has 

 fallen as rain. Some of this water must evidently be many months 

 journeying in the earth before reaching the river and a small part of 

 it perhaps even years. But at last it emerges, Joins the river and 

 reaches the ocean. 



You may imagine that now its useful work is done. By no means. 

 For let us see what happens to it after reaching the ocean. We have 

 already seen that it carries a large burden of mud with it. This it 

 drops gradually, some near the shore and some far out at sea. Thus 

 it coats the sea bottom vnth clay, which in the course of ages solidi- 

 fies into rocks and these rocks will in still more distant ages probably 

 be raised to the surface to form new continents. Some of the mate- 

 rials carried by the rivers into the ocean also serve as food for the 

 creatures that live in the ocean. 



This, however, is not the only useful work which the currents in 

 the ocean do. Let us consider, for instance, the water carried down 



