20 FRAGMENTS OF SCIENCE. 



it the enhancement of the other, the total value of the 

 property remaining unchanged. 



The considerations here applied to gravity apply 

 equally to chemical affinity. In a mixture of oxygen 

 and hydrogen the atoms exist apart, but by the appli- 

 cation of proper means they may be caused to rush to- 

 gether across that space that separates them. While 

 this space exists, and as long as the atoms have not be- 

 gun to move towards each other, we have tensions and 

 nothing else. During their motion towards each other 

 the tensions, as in the case of gravity, are converted into 

 vis viva. After they clash we have still vis viva, but 

 in another form. It was translation, it is vibration. 

 It was molecular transfer, it is heat. 



It is possible to reverse these processes, to unlock 

 the combined atoms and replace them in their first 

 positions. But, to accomplish this, as much heat would 

 be required as was generated by their union. Such re- 

 versals occur daily and hourly in nature. By the solar 

 waves, the oxygen of water is divorced from its hydrogen 

 in the leaves of plants. As molecular vis viva the 

 waves disappear, but in so doing they re-endow the 

 atoms of oxygen and hydrogen with tension. The 

 atoms are thus enabled to recombine, and when they 

 do so they restore the precise amount of heat consumed 

 in their separation. The same remarks apply to the 

 compound of carbon and oxygen, called carbonic acid, 

 which is exhaled from our lungs, produced by our fires, 

 and found sparingly diffused everywhere throughout 

 the air. In the leaves of plants the sunbeams also 

 wrench the atoms of carbonic acid asunder, and sacri- 

 fice themselves in the act; but when the plants are 

 burnt, the amount of heat consumed in their produc- 

 ,tion is restored. 



This, then, is the rhythmic play of Nature as re- 



