178 SCIENCE AND IMMORTALITY 



Oxygen is a most sociable element and weds 

 on every opportunity, the wedding being often 

 celebrated by visible flame, e.g. ordinary com- 

 bustion. Nitrogen is what is known as an inert 

 gas and weds only under compunction. It is 

 also a constituent of gunpowder, dynamite, and 

 most explosives. Hydrogen is a gas so light 

 and active that the earth is unable to retain it, 

 and it flies away into space. In combination with 

 oxygen, hydrogen forms water. 



Protoplasm is thus seen to consist of three 

 remarkable gases and a remarkable solid. It is 

 very strange to consider that there are about 

 eighty elements, and that four, and only four, are 

 essential to life. One would think that silicon, or 

 gold, or silver might do as well as carbon, but 

 they are quite useless ; without carbon, life cannot 

 be. Why should these four elements have such a 

 remarkable career ^ We cannot tell ; but we can 

 guess at least that the power possessed by carbon 

 of linking atoms together may l^e useful ; that 

 the explosive tendencies of nitrogen may give 

 protoplasm its mobility, and that the chemical 

 activity of oxygen must be serviceable. What- 

 ever the reason, these four elements are the 

 bearers of life. 



Where do they come from } They are found 

 everywhere. The ocean, as we have seen, is 



