CHANGES IN THE SOIL. 249 



it in certain chemical proportions, you have nitric acid. It 

 finds in the soil carbon, unites with it, and you have carbonic 

 acid. 



So you have made by the action of the oxygen of the 

 air in the soil, first, oxides, and all the materials of food for 

 the growth of 3^our plant ; and, next, j^ou have the corroding, 

 destroying acids, wliich now act in this way. Your potash, 

 your soda, your lime, &c., which were in the soil, were more 

 generally in the form of silicates. Lime, potash, soda, mag- 

 nesia, united with silicic acid, which are as insoluble as j'on- 

 der window-glass, are now touched with carbonic acid, and 

 the lime leaves the silicic acid, and goes to the carbonic acid. 

 The potash leaves the silicic acid, and goes to the carbonic 

 acid, and so on ; a great round of changes, each one of which 

 wrings out of these silicates that we call the minerals of the 

 soil, — wrings out of them lime and potash and soda, and 

 phosphoric acid and magnesia, which we find is the material 

 which we call " ash " in the plant, and which by this process 

 has been changed from insolubility to solubility, and becomes 

 available for the plant, that its structure may be built up. 



But what has the plant to do with this ? What has tlie 

 plant to do with cither sterility or fertility ? Much, every 

 way. Now, whatever the mode of action, whatever may be 

 the power and force of the air in converting this soil from 

 its insoluble to its soluble condition, the living plant on the 

 soil re-enforces, strengthens, and increases it many fold. 

 The rootlets of the living plant, working upon the sur- 

 face of the particles of the soil, re-enforce and strengthen, 

 and make more powerful, all these other natural agencies. 

 We place the plant upon the soil. Its rootlets permeate 

 the whole surface, clinging to the particles by the root- 

 hairs, incasing them, holding on to them and doing what? 

 Gathering water ; making a current of water, or increasing 

 the force of that current which passes over the particles 

 of the soil and thus removes a solution, giving place for 

 another portion of water to come from the soil beneath, 

 and thus constantly keeping up a circulation of this mate- 

 rial, removing it as formed, and depositing it in the plant 

 above ; so that the action of the oxygen and the action of 

 the acids of the soil is re-enforced and made more active and 

 more potent by the root-action in the soil. 



