378 FRAGMENTS OF SCIENCE. 



from which it fell. There is no energy generated by the 

 machinery: the work performed by the water in descend- 

 ing is merely the parceling out and distribution of the 

 work expended in raising it. In precisely this sense is all 

 the energy of plants and animals the parceling out and 

 distribution of a power originally exerted by the sun. In 

 the case of the water, the source of the power consists in 

 the forcible separation of a quantity of the liquid from a 

 low level of the earth's surface, and its elevation to a 

 higher position, the power thus expended being returned 

 by the water in its descent. In the case of vital phe- 

 nomena, the source of power consists in the forcible sepa- 

 ration of the atoms of compound substances by the sun. 

 We name the force which draws the water earthward 

 " gravity, "and that which draws atoms together " chemical 

 affinity; " but these different names must not mislead us 

 regarding the qualitative identity of the two forces. They 

 are both attractions; and, to the intellect, the falling of 

 carbon atoms against oxygen atoms is not more difficult of 

 conception than the falling of water to the earth. 



The building up of the vegetable, then, is effected by 

 the sun, through the reduction of chemical compounds. 

 The phenomena of animal life are more or less complicated 

 reversals of these processes of reduction. We eat the 

 vegetable, and we breathe the oxygen of the air; and in our 

 bodies the oxygen, which had been lifted from the carbon 

 and hydrogen by the action of the sun. again falls toward 

 them, producing animal heat and developing animal forms. 

 Through the most complicated phenomena of vitality this 

 law runs: the vegetable is produced while a weight rises, 

 the animal is produced while a weight falls. But the ques- 

 tion is not exhausted here. The water employed in our 

 first illustration generates all the motion displayed in its 

 descent, but the form of the motion depends on the char- 

 acter of the machinery interposed in the path of the water. 

 In a similar way, the primary action of the sun's rays is 

 qualified by the atoms and molecules among which their 

 energy is distributed. Molecular forces determine the 

 form which the solar energy will assume. In the separation 

 of the carbon and oxygen this energy may be so conditioned 

 as to result in one case in the formation of a cabbage, and 

 in another case in the formation of an oak. So also, as 

 regards the reunion of the carbon and the oxygen, the 



