116 CHEMICAL ACTION. 



indeed, demonstrable, eannot fail to impress every mind 

 with its beauty, and probable correctness. 



In the growth of a tree, its wood and all its products- 

 are the result of certain external forces effecting chemi- 

 cal changes. Carbonic acid is decomposed, the carbon 

 is retained, and oxygen given off, and assimilations of a 

 complex character are in constant progress to produce 

 the various compounds of oxygen, hydrogen, nitrogen., 

 and carbon. 



Every condition of organised forms is due to the exter- 

 nal excitation of light and heat, and in the chemical 

 changes which take place, an equivalent of these prin- 

 ciples, or powers it signifies but little according to which 

 view we may regard them is absorbed, and retained as 

 essential to the condition of the matter formed. Let us 

 confine our attention to wood although the position 

 applies equally to every organic product. A cubic foot 

 of wood is formed by the decomposition of a certain 

 quantity of carbonic acid, by the vital function of the 

 plant, excited by the solar rays, which are involved in 

 the mass which nature by " her wondrous alchemy" has 

 made. Eventually this cubic foot of wood is subjected 

 to a process of chemical change combustion ; by the 

 application of a single spark, and in the disintegration 

 of the wood, its carbon combining with oxygen to form 

 carbonic acid, its hydrogen to form water, which is re- 

 turned to the air, a large amount of light and heat is pro- 

 duced. This is exactly equivalent to the amount which 

 was engaged in its formation. Indeed, the sunshine which 

 fell upon the leaves of the forest tree, of which the log 

 formed a part, has been hoarded up, and we again deve- 

 lope it in its original state of heat and light. 



The vast coal beds of England were formed by the 

 rapid growth and quick decay of a peculiar class of 

 plants under the influence of a tropical sun. They have 

 been buried myriads of ages, under hundreds of feet of 

 sandy rock. By the industry of the miner the coal 



