124 WRITINGS OP JOSEPH HENRY. [1855- 



and it may be to undergo the same changes many times in 

 succession. The earthy materials are again returned to the 

 earth, and all the conditions, as far as the individual plant 

 which we are considering is concerned, are the same as they 

 were at the beginning. The absorption of power in the de- 

 composition of the carbonic acid gas, and its evolution again 

 when the re-composition is produced of the same atoms, is 

 precisely analogous to that which takes place in forcibly 

 separating the poles of two magnets, retaining them apart 

 for a certain time, and suffering them to return by their 

 attractive force to their former union. The energy developed 

 in the approach of the magnets towards each other is just 

 equal to the force expended in their separation. 



By extending this reasoning to the vast beds of coal which 

 are stored away in the earth, we are brought irresistibly to 

 the conclusion that the power which is evolved in the com- 

 bustion of this material, now so valuable an agent in the pro- 

 cesses of manufacture and locomotion, is merely the equiv- 

 alent of the force which was expended in de-composing the 

 carbonic acid which furnished the carbon of the primeval 

 forests of the globe; and that the power thus stored away 

 millions of years before the existence of man, like other pre- 

 ordinations of Divine Intelligence, is now employed in 

 adding to the comforts and advancing the physical and in- 

 tellectual well-being of our race. 



In the germination of the plant a part of the organized 

 molecules runs down into carbonic acid to furnish power for 

 the new arrangement of the other portion. In this process 

 no extraneous force is required: the seed contains within 

 itself the power and the material for the growth of the new 

 plant up to a certain stage of its development. Germination 

 can therefore be carried on in the dark, and indeed the 

 chemical ray which accompanies light retards rather than 

 accelerates the process. Its office is to separate the atoms of 

 carbon from those of oxygen in the decomposition of the car- 

 bonic acid, while that of the power within the plant results 

 from the combination of these same elements. The forces 

 are therefore antagonistic, and hence germination is more 



