68 FEAGMENTS OF SCIENCE. 



cules are permitted to bring their forces into free play, 

 arranges itself, under the operation of these forces, into 

 forms which rival in beauty those of the vegetable world. 

 And what is the vegetable world itself, but the result of 

 the complex play of these molecular forces ? Here, as 

 elsewhere throughout nature, if matter moves it is force 

 that moves it, and if a certain structure, vegetable or 

 mineral, is produced, it is through the operation of the 

 forces exerted between the atoms and molecules. 



The solid matter of which our lead and silver trees 

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

 transparent liquid ; the solid matter of which our woods 

 and forests are composed is also, for the most part dis- 

 guised 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 

 fibre. The watery vapour 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 vapour 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 expression 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. 



