THE PLEASURES OF SCIENCE 



it is as if two and two made three or five, as if one 

 gathered grapes of thorns, and figs of thistles. What 

 can be more marvelous than the elementary fact 

 that two invisible and tasteless and odorless gases, 

 oxygen and hydrogen, unite chemically in certain 

 proportions, producing water a body totally 

 unlike either? Oxygen supports combustion, hy- 

 drogen burns freely, and yet water quenches fire 

 the magic of chemical reactions truly ! 



Think of the terrific forces bound up in chemical 

 compounds which fire or a blow releases! We can 

 form no mechanical image of such things. Our 

 springs and coils and weights may hold great forces 

 in leash, but no more than what we put into them. 

 The clock in running gives back or uses up the 

 forces you put into it in winding, but the explosive 

 compound releases energy that is of chemical origin; 

 it is created then and there through the action of 

 the law of chemical affinity. Nitrogen is the princi- 

 pal element in all the terrible explosions, and yet 

 nitrogen is the most inert, lazy, or indifferent of 

 the primary elements. It is reluctant to combine 

 with any other element. Mixed with oxygen, the 

 two form our air. Were it suddenly to unite with 

 oxygen chemically, of which there is no danger, our 

 atmosphere would disappear; and we should have 

 in its place a sea of ammonia or of nitrous acids. 



It is a kind of revelation when we know that the 

 greater part of the solid earth is made of gas. A 

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