258 



On Agricultural Chemistry. 



fairly calculate upon as standing in the way of such a consumma- 

 tion, as well as the physiological and commercial considerations 

 which would be involved in its influence, are such that we need 

 not now anticipate the result. Again, the supposition that the 

 artificial manures at present at our command, might, if directly 

 applied to the growth of corn, be adequate to its sufficient pro- 

 duction throughout the country, without the aid of green crops 

 in feeding, is satisfactorily met by such calculations as the fol- 

 lowing: — The county of Norfolk is said to comprise 1,338,880 

 acres of land : suppose one-half of this to be cultivated on the 

 four-course system, 334,720 acres will be under corn every year. 

 I believe it will not be considered an exaggeration to say that 

 cultivation in this county has increased the natural produce of 

 corn by 10 bushels per acre; and according to my calculations, it 

 would require something like 50 lbs. of ammonia to be supplied 

 in any artificial manure to produce this increase of corn ; and 

 considering ] ton of Peruvian guano to contain 224 lbs. of am- 

 monia, it would require an importation of 74,714 tons to supply 

 the necessary amount for one year. This calculation affords some 

 idea of the value of a rotation of crops. 



It is not very difiicult to arrive at a correct knowledge of the 

 action and value of artificial manures. They are generally com- 

 posed of two or three ingredients in a state of concentration, and 

 are far more rapid in their action upon plants than the manure 

 which is produced by animals. They can therefore be applied 

 with greater success to those crops which are required in an arti- 

 ficial condition, and the growth of which cannot be too vigorous. 



If there be any truth in my experiments, all hope of obtaining 

 annual crops of corn by means of mineral manures must be for 

 ever abandoned. The employment of potash, soda, magnesia, 

 and silica, has been suggested by chemists, from an imperfect 

 knowledge of practical agriculture. Having found these sub- 

 stances in the ash of the plants, they have concluded that the soil 

 cannot supply them in sufficient quantity. I could bring forward 

 a great number of experiments, tried at my suggestion upon 

 various soils, which would prove that alkaline manures were quite 

 incompetent to remedy the exhaustion from which they suffered ; 

 but the general practice of the best agriculturists is more con- 

 vincing than a thousand such experiments. Take the case of a 

 soil which has been in the hands of a farmer who has removed 

 from his land successive grain crops, and who has also sold part 

 of his straw and hay, bringing back perhaps a little soot, or some 

 light manure. This system would exhaust the soil of its alkalies 

 to the greatest extent possible. Should it then come into the 

 possession of a man of capital and experience, he may in a few 

 years bring it into high condition without imparting to it a pound 



