OBJECTIONS TO THE THEORY OF LIEBIG. 147 



of injury. Of course, the richer a soil is in humus, the more 

 injurious must its effects be upon the crop ! 



3. This theory does not give a correct view of the quantity 

 of water in the soil. Rains are by no means the only source 

 of water. All vegetable bodies, according to Liebig, and 

 others, in the process of decay, yield carbonic acid and wa- 

 ter. For, although water is decomposed, it is but a small quan- 

 tity, compared with that which is formed by the union of the 

 oxygen of the air and the hydrogen of the vegetable matter. 

 From this latter source, not noticed by Liebig, a quantity of 

 water is furnished, sufficient to hold in solution a larger quan- 

 tity of humates, than the theory supposes. 



This is a perfect answer to the assertion, that the rains do 

 not furnish a sufficient quantity* of water to hold the humates 

 in solution. In fact, it is highly probable, that the plants, on 

 an acre of soil, take up by their roots and transpire through 

 their leaves, a larger quantity of water, during any given time, 

 than falls during the same time upon an equal surface. But 

 if water dissolves any portion of the humates, it must be the 

 means of conveying to the plant a portion of their carbon. 



4. This theory entirely overlooks the influence of living 

 plants upon the alkalies in the soil. 



The vegetable, in connection with the soil and water, forms 

 a galvanic battery, by which the alkalies are eliminated. 

 These alkalies, coming in contact with humus or geine, ren- 

 der it soluble. This is a farther means of introducing hu- 

 mates into the organs of plants,t and hence a part of the car- 

 bon must be derived from this source. 



5. "Vegetable and animial manures," says Berzelius, " be- 

 come changed, after a while, into crenic, apocrenic and hu- 

 mic acids, in order to supply what has been removed by the 



* See Dana's Muck Manual, p. 225. 



t See Dr. Dana's Letter to Prof Hitchcock, in the Final Report of 

 the Geology of Massachusetts. Also, Appendix to Liebig, 2d edit. 



