WATER 141 



mineral salts in the earth. Water has aided in making 

 the deposits of mineral salts found in the mountains as 

 well as in lowlands. Through evaporation and through 

 mixture with substances that will not remain together 

 in solution, the salts that the water has dissolved have 



A VALLEY MADE BY EROSION 



been deposited in the bed of lakes or fissures in the rocks 

 which the water once covered. If the larger part of the 

 mineral in solution was an iron oxide, the deposit is a bed 

 of iron ore. Many of the gold and silver veins in the 

 Rocky Mountains were formed by the action of water. 

 Mineral veins are also sometimes formed by precipita- 

 tion. Ask your teacher how to form a precipitate, by 

 pouring two solutions together. 



If the surface water that is slightly acid flows into the 

 ground and comes in contact with a layer of limestone, 

 the acid will cause the limestone to be decomposed and 

 gradually carried away by the water. After this action 



