SCIENCE OF COMMON THINGS. 



What is water ? "What is hard water ? 



sides of a vessel or on its bottom, or on any body im- 

 mersed in it, is nearly one pound on the square inch 

 for every two feet of depth. 



313 What is water? 



Water is a fluid composed of oxygen and hydrogen, 

 in the proportion of eight parts of oxygen to one part 

 of hydrogen. 



314 Why is water fluid? 



Because its particles are kept separate by latent 

 heat ; when a certain quantity of this latent heat is 

 driven out, water becomes solid, and is called ice. 



By increasing its latent heat, the particles of water are again subdivided 

 into invisible steam. 



315 Why is spring water generally called "hard water?", 



Because it is laden with foreign matters, and will 

 not readily dissolve substances immersed in it. 



316 What makes spring or well water geneartty hard ? 



"When it filters through the earth, it becomes im- 

 pregnated with sulphate of lime, carbonate of lime, 

 carbonic acid, magnesia, and many other impurities, 

 from the earths and minerals with which it comes in 

 contact. 



31 7 What is the cause of mineral springs ? 



"When water trickles through the ground, it dissolves 

 some of the substances with which it comes in contact ; 

 if these substances are retained in solution, the water 

 will partake of their mineral character. 



318 When is a mineral water called a chalybeate ? 



When it contains iron, in some form, dissolved in it. 



319 Mineral springs exist in all parts of our country : what is the 

 nature of the substances contained in them ? 



The great majority of them are only impregnated 

 with iron, salt, or sulphur. Some few, however, con- 

 tain many different substances, as the mineral waters 

 of Saratoga. 



3J3O Why are springs containing iron in large quantities beneficial to 

 tome invalids ? 



Because the iron contained in the water acts as a 



