MATTER AND FORCE. 393 



The solid matter of which our lead and silver trees 

 were formed was, in the first instance, disguised in a trans- 

 parent liquid; the solid matter of which our woods and 

 forests are composed is also, for the most part, disguised in 

 a transparent gas, which is mixed in small quantities with 

 the air of our atmosphere. This gas is formed by the 

 union of carbon and oxygen, and is called carbonic acid 

 gas. The carbonic acid of the air being subjected to an 

 action somewhat analogous to that of the electric current 

 in the case of our lead and silver solutions, has its carbon 

 liberated and deposited as woody fiber. The watery vapor 

 of the air is subjected to similar action; its hydrogen is 

 liberated from its oxygen, and lies down side by side with 

 the carbon in the tissues of the tree. The oxygen in both 

 cases is permitted to wander away into the atmosphere. 

 But what is it in nature that plays the part of the electric 

 current in our experiments, tearing asunder the locked 

 atoms of carbon, oxygen, and hydrogen? The rays of the 

 sun. The leaves of plants which absorb both the carbonic 

 acid and the aqueous vapor of the air, answer to the cells 

 in which our decompositions took place. And just as the 

 molecular attractions of the silver and the lead found ex- 

 pression in those beautiful branching forms seen in our 

 experiments, so do the molecular attractions of the liberated 

 carbon and hydrogen find expression in the architecture of 

 grasses, plants, and trees. 



In the fall of a cataract and the rush of the wind we 

 have examples of mechanical power. In the combinations 

 of chemistry and in the formation of crystals and vege- 

 tables we have examples of molecular power. You have 

 learned how the atoms of oxygen and hydrogen rush to- 

 gether to form water. I have not thought it necessary to 

 dwell upon the mighty mechanical energy of their act of 

 combination; but it may be said, in passing, that the 

 clashing together of 1 Ib. of hydrogen and 8 Ibs. of oxygen 

 to form 9 Ibs. of aqueous vapor, is greater than the shock 

 of a weight of 1,000 tons falling from a height of 20 feet 

 against the earth. Now, in order that the atoms of oxygen 

 and hydrogen should rise by their mutual attractions to 

 the velocity corresponding to this enormous mechanical 

 effect, a certain distance must exist between the particles. 

 It is in rushing over this that the velocity is attained. 



