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 
