40 



On Agricultural Chemistry. 



from the atmosphere ;" and, indeed, that any increased produce 

 of it, such as British agricuhure (itself so artificial) demands, 

 cannot be obtained independently of an artificial accumulation 

 of nitrogen within the soil. 



Of those crops of rotation, on the other hand, where the effect 

 of mineral manures is characteristically to increase the assimilation 

 of nitrogen from atmospheric sources, and by virtue of which pro- 

 perty they indeed become subservient to the increased growth of 

 grain, the apparent demand for these substances is not only gene- 

 rally not such in kind as would be indicated by an analysis of their 

 ashes, but is frequently much greater as to quantity than can be 

 accounted for by any idea of merely supplying what is to become 

 an actual constituent of the crop. If, then, we would attain by the 

 aid of science a rational system of agriculture, the actual facts of 

 the art itself, as well as the indications of direct experiments in 

 the field, and a study of the functional actions of plants and 

 animals, must receive a due share of our attention. In fact, 

 chemistry alone will do nothing for practical agriculture. 



Note. — This important paper so completely establishes what 

 I wrote in our last Number on the entire failure of the Mineral 

 Theory as a guide to the use of manures in practical farming, that 

 I need only express my regret for the annoyance which its author 

 has publicly expressed, as I am told, at those remarks. In 

 cautioning the English farmer against what seemed to me a dan- 

 gerous error, I certainly endeavoured to do justice to the real 

 discoveries of Baron Liebig. Since the experiments, however, of 

 Mr. Lawes and Dr. Gilbert have, as I hear, been disputed, 

 I am bound to say that my confidence in the scrupulous accuracy 

 of those gentlemen has been only strengthened by a subsequent 

 visit to Rothamstead, in company with that eminent philosopher 

 Mons. Dumas. The extent of the experimental ground — the 

 expenditure at which it has been kept up — the perseverance with 

 which, year after year, it has been maintained, are such as might 

 rather be expected from a public institution than a private land- 

 owner, and render Rothamstead, at present, the principal source 

 of trustworthy scientific information on Agricultural Chemistry. 



PlI. PUSEY. 



