WATER 189 



kettles, the ocean, and from other bodies of water as 

 well, the salt and other substances in solution of 

 course being left behind. When clouds of this moisture 

 come in contact with cold currents of air, condensa- 

 tion ensues, and water falls to the ground in the form 

 of rain, hail, or snow. Rain would be as pure as dis- 

 tilled water, if it did not bring along ammonia, dust, 

 and other substances that are in the air. How clean 

 and pure the air seems just after a hard rain storm ! 

 This is because the rain has given it a thorough 

 cleansing. 



Much of the water that falls from the clouds drains 

 into small streams, and finally reaches the ocean. 

 A considerable quantity soaks down into the earth, 

 however, collecting in some rocky region through 

 which it cannot pass. Here it forms the sources of 

 various wells, or bubbles out of lower ground in the 

 form of springs. In passing through the ground, the 

 substances brought with it from the air are filtered 

 out, but it oft'en dissolves others in the earth through 

 which it passes. Water that has taken up considerable 

 lime or other mineral matter in passing through the 

 earth is called hard water. That which has very little 

 mineral substance in solution is called soft water. 

 Some waters have taken up salts, sulphur, or other 

 mineral matter that gives them valuable medicinal 

 qualities, and so sanitariums are built near such springs, 

 and their waters often have a large sale. 



Why does the housewife prefer soft water for wash- 



