74 FRAGMENTS OF SCIENCE 



our earth " brute matter, 7 ' as Dr. Young, in his u Night 

 Thoughts," is pleased to call it when its atoms and 

 molecules 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, vege- 

 table 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 vapor of the air is subjected to simi- 

 lar 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 wan- 

 der away into the atmosphere. But what is it in nature 

 that plays the part of the electric current in our experi- 

 ments, tearing asunder the locked atoms of carbon, oxy- 

 gen, and hydrogen? The rays of the sun. The leaves 

 of plants, which absord both the carbonic acid and the 

 aqueous vapor of the air, answer to the cells in which 



