AQUEOUS AGENCIES. 67 



ground moraine. In addition to this, as soon as it divides 

 at the land-margin into separate glaciers which run down 

 into the fiords, each separate glacier receives its burden 

 of material from the cliffs on each side of the fiord, and 

 thus becomes loaded with earth and stones. The ice- 

 bergs, therefore, carry away immense quantities, both 

 lying on their surface and frozen in their lower parts. 

 These are dropped as they melt. Thus, the land of 

 Greenland is being cut down by glaciers and carried away 

 by icebergs, and strewed all over the bottom of the At- 

 lantic as far south as 50 to 40 north latitude. The 

 materials thus dropped over the sea-bottom are similar 

 to those borne by glaciers, and dropped in their pathway, 

 except that they are carried much farther, and also that 

 they are more or less sorted and stratified by dropping 

 through water. Large blocks perched in insecure posi- 

 tions would not probably occur. 



Therefore, smooth, striated, moutonneed rocks, perched, 

 angular blocks, and terminal moraines cannot be produced 

 by icebergs, but are wholly characteristic of glaciers. 

 The importance of this discussion will be seen when we 

 come to speak of the Glacial epoch. 



SECTION IV. CHEMICAL AGENCY OF WATER. 



It will be remembered that we divided the agency of 

 water into mechanical and chemical. We have now fin- 

 ished the former, and are ready to take up the latter. 

 Previous to doing so, however, there is a preliminary sub- 

 ject of great interest, viz., underground waters. And 

 here we return again to the domain of familiar observa- 

 tion, for every student may observe for himself much that 

 follows : 



Underground Waters and Origin of Springs. 



As already said (page 18), of the water which falls by 

 rain and snow, a part runs off the surface, producing uni- 



