1847.J Agiicultural Chemistry. 149 



7. Before ofTering these reasons, let the arguments be consider- 

 ed which seem to support the doctrine of Liebig. 



8. The growth of a foreat, and the amount of carbon produced. 

 Admitting that this carbon is derived from the atmosphere, has 

 any proof been offered that the growth of that forest would not 

 have been greatly augmented, if the whole earth under it had 

 been manured to the perfection attained on the fields of many ag- 

 riculturists? 



9. The removal of nitrogenous products, as wheat, corn, bearis, 

 &c. Admitting that the carbon and nitrogen are derived from the 

 atmosphere, has experiment ever proved, that a soil containing all 

 the other inorganic elements ot the sujiport of plants will produce 

 in equal quantity with that which, besides the same inorganic ele- 

 ments, is abundantly dressed with vegetable and animal manures? 

 Besides, how do night soil, guano, &c., produce these wonderful 

 results, if manures have no importance in supplying carbon and 

 nitrogen to plants? 



10. Increase of products by som.e inorganic substance, as ashes, 

 without other manures. In such a case, has it been known that 

 the soil was destitute of vegetable and animal matter? If not, 

 then ashes may have been the material to increase the power of 

 the plants to take up moie vegetable matter from the earth, as 

 well as more nutriment from the atmosphere. If the soil was des- 

 titute of vegetable matter, where is the proof that the addition of 

 vegetable and animal manures with the ashes, would not have pro- 

 duced a still greater increase? Until the contrary shall be proved 

 by experiment, the adduced fact cannot be conclusive proof. The 

 same may be remarked of the use of other inorganic substances 

 in other s'milar circumstances. This is corroboi'ated by the ac- 

 knowledged but imperfect growth of vegetables in earth destitute 

 of vegetable or animal matter. 



11. It should have been remarked, that the doctrine of Liebig 

 is often supposed to imply that the carbon and nitrogen are taken 

 up only by the leaves of plants, being derived directly from the 

 atmos])here. But. he intended to include also that introduced by 

 the roots, which had been carried to the earth in rain and snow. 

 For he declares afterwards, that "the roots and other parts of it 

 (a plant), which possess the same power, absorb constantly water 

 and carbonic acid."* The same is to be admitted in respect to 

 ammonia, as it must in the same ways find a passage into the 

 plant. And this is the more necessary to be admitted, as, accord- 

 ing to Prof. Horsford, Dr. Krocker has ascertained that a large 

 amount of ammonia exists in all the common soils. This varies 

 in different soils, from 3373 to 9751 pounds of ammonia in an 



* Again he says, " The carbonic acid, which has been absorbed by the 

 leaves and by the roots, together with water," &c.; p. 33. 



