ACTION OF SALTS. 1^9 



sent themselves in a new relation, in which, alone, they may- 

 be said to be stimulants or excitants. Plants and soil act, 

 it may be supposed, for illustration, by forming galvanic 

 batteries, or piles with each other. The most active element 

 in the pile, is the growing plant. It is an acknowledged fact, 

 that chemical action, if not the source, is ever attended by 

 electrical effects. An acid, in contact with an all^ali, or 

 metal, always produces chemical action ; but the silicates of 

 the soil are already combinations of acid and metals ; hence, 

 as such, they have no tendency to act on each other. If 

 there be added to these a salt or an acid, chemical action, 

 decomposition begins. The electricity is, we may say, 

 excited by salts ; they are in this sense, and in no other, 

 excitants or stimulants. The very first act of vegetation, 

 the germination of seeds, induces this electric action, this 

 decomposition of the elements of soil. Germination pro- 

 duces carbonic acid, by decomposing water. This has been 

 so abundantly proved, by late experiments in France, that it 

 appears to be a good argument against the theory, that the 

 only action of humus is its production of carbonic acid, to 

 supply the wants of the plant, before nature has clothed it 

 with those organs of aspiration, the leaves, by which the 

 carbonic acid is withdrawn from the air. It seems hardly 

 probable that nature should require the presence of humus 

 or geine, merely as a laboratory of carbonic acid, to supply 

 the wants of the young plant. The very first act of life in a 

 seed is to evolve carbonic acid, by its carbon combining 

 with oxygen of air, and its second act is to decompose 

 water. Its oxygen combines with the carbon of the seed ; 

 a single bean produces many times its bulk of carbonic acid 

 gas, and in the soil would surround itself with an atmosphere 

 of carbonic acid. This evolved, begins its action upon the 

 silicates. The living seed begins the electric action, and the 

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