1846.J Theory of Agriculture. 7 



is then conveyed, after due elaboration, to distant parts of the 

 individual. 



The views of Liebig are based on experiments instituted 

 by Saussure, for the purpose of ascertaining the fact of the ab- 

 sorption of carbonic acid by the leaves of plants. Besides, 

 Liebig states that the carbon of soils, that of humus for in- 

 stance, is comparatively insoluble, and hence cannot be receiv- 

 ed into the vegetable tissue. Humus or mould, requires for 

 solution 2500 parts of water, converted into humic acid it enters 

 into combination with the alkalies and earths, and forms hu 

 mates of lime, potash, soda, magnesia, &,c. ; these are more 

 soluble than humic acid; — besides, humic acid is only soluble 

 when recently precipitated. When dried, or when it has been 

 exposed to frost, it becomes comparativeh'- insoluble. When 

 mould has been acted upon by 100,000 times its weight of wa- 

 ter the fluid remains colorless, and contains but a trace of it in 

 solution. 



Hence, it is the opinion of Liebig, that humus, as it exists iu 

 the soil, does not yield the smallest quantity of nourishment to 

 plants. 



To present the case, however, in a still stronger light. Lie- 

 big goes on to show by calculation, that all the salts of humic 

 acid which are found in the soil are insufficient to furnish 

 nutriment to growing vegetables ; for a Hessian acre of wood- 

 land produces annually 2920 lbs. of dry wood, which contains 

 6.17 lbs. of metallic oxides. But reasoning from the composi- 

 tion of the humates only, 100 lbs. of carbon will be formed in 

 one year on an acre of woodland, if there were no other 

 source of carbon than that of the soil in which they grow, 

 which of course makes a great deficiency of matter, for there 

 is really produced no less than 2920 lbs. of wood, the greater 

 part of which is carbon. 



To fortify his position still farther, Liebig goes on to speak 

 of the produce of an acre of wheat, the straw of \vhich amounts 

 to 1961 lbs., the composition is known to be the same as woody 

 fibres, but the quantity of woody of woody fibre which can 



