SCIENCE 



in the soil in the shape of air, but only certain plants 

 can lay hold of it. Minute organisms can do it, and 

 Niagara can do it, the thunderbolt can do it, but 

 what else? 



§ 



After we have divided and subdivided matter 

 mechanically to the utmost point, and reached the 

 molecule, science takes the further step and divides 

 it chemically and reaches the atom. Divide a mole- 

 cule of water chemically and we get the atoms of 

 hydrogen and oxygen — two of one to one of the 

 other. Divide a molecule of common salt chemically 

 and we get one atom of sodium and one of chlorine. 

 Divide a molecule of lime chemically, and we get 

 one atom of calcium and one of oxygen. Oxygen is 

 one of two main elements in things so diverse as 

 lime, air, and water — the magic of chemical com- 

 binations! When we breathe, we take into our lungs 

 one of the main constituents of the rocks and of the 

 solid ground under our feet. Our blood is red by 

 virtue of the element that helps hold the world 

 together. We eat and bum the stuff of diamonds. 



The ring of six carbon atoms that make up the 

 molecule of the diamond, and that is supposed to 

 account for its hardness — how imagmary it is! 

 The molecule of most of the elementary gases con- 

 sists of two atoms of these elements. The molecules 

 of oxygen and nitrogen in the air are not combined 

 chemically, but are only mechanically mixed. 



263 



