MINERALS AND CRYSTALS 185 



part of the very rock itself, yet a part that we can- 

 not see. Salt is a part of a loaf of bread which we 

 cannot see or take away when once it has mixed 

 into the bread dough. But if that loaf of bread 

 were turned into a rock, water could go through it 

 and take out the salt. 



If you put a pebble into a glass of water it would 

 still be a pebble. But if you should put a lump of 

 salt into the glass of water, would it still stay there 

 and be a lump of salt? Of course it would not. 

 We all know that salt dissolves in water. It is there 

 just the same, for the water tastes salt, but we can- 

 not see it at all, or feel it. The water holds it in 

 solution, we say, and it will hold it just as long as 

 there is water enough to do it. When the water 

 evaporates it leaves the salt behind and we have 

 our lump of salt again, only changed into small 

 grains like sand. 



Now this is the difference between the work done 

 by the water which flows off the surface of the earth 

 and that which sinks so gradually in toward the 

 center. The noisy, laughing little brook takes up 

 rocks and pebbles and carries them along with it, 

 but the quiet little underground drops, all nice and 

 warm from their journey into the deep recesses of 

 the earth, gently coax away the minerals which are 

 in the very heart of the rocks. Very softly and gently 

 they sink through the rocks, and when they get to a 

 crack in the rock or a small hole hke an empty bubble, 

 they deposit, or drop, the atoms they have been 

 carrying. Only, instead of dropping them any- 

 where and hurrying on, as does the water in the 



