242 



On Agricultural CheDiistry . 



tween the French and German chemists, is perhaps the most 

 important to agriculture which chemistry can solve. It affects 

 the whole economy of cultivation, and the final solution of it must 

 materially influence the actions of all practical agriculturists. 

 With regard to the most important crop (wheat), my own experi- 

 ments are so decisive, and through the whole series the results 

 are so uniform, that it is hardly possible to have two opinions on 

 the subject; and, what is still more important, they are in accord- 

 ance with the dictates of reason and the practical experience of 

 agriculture. The first year's experiments were drawn out prin- 

 cipally with the view of ascertaining how far mineral manures 

 were capable of restoring the fertility to a soil of which it had 

 been deprived by repeated cropping. On the space of ground 

 which was not manured, the acreage yield was as follows : — 



Grain, 16f bushels; straw, 1120 lbs. 

 This may be considered as the natural produce of the soil, sub- 

 ject only to the atmospheric influence of that particular season. 

 The next experiment was with 700 lbs. of superphosphate of 

 lime, which gave — 



Grain, 16f bushels; straw, 1116 lbs. 



The superphosphate of lime employed in these experiments was 

 made from calcined bone only^, and was therefore strictly a 

 mineral manure. By comparing this experiment with the last, 

 it will be seen that no increase of produce was obtained. 



The effect of superphosphate of lime upon wheat has been the 

 subject of many experiments, and in some instances it has been 

 employed vvith remarkable success. It becomes therefore of im- 

 portance to inquire what was the probable cause of its inutility in 

 this instance. Besides phosphoric acid and lime, the ash of 

 wheat and wheat straw contains potash, magnesia, soda, and 

 silica ; and as superphosphate of lime contains none of these sub- 

 stances, its failure in this case may be attributed either to the 

 absence of these minerals in the soil, or to a deficiency of azotized 

 or other organic matter. 



The average results obtained by other mineral manures are 

 given below :* — 



* The terms superphosphate of lime, phosphate of potass, phosphate of 

 soda, and phosphate of magnesia, by which it is convenient to designate 

 the manm-es, are not to be understood as representing the pure chemical 

 substances bearing those names. The composts were formed by acting 

 upon bone-dust by means of sulphuric acid, in the first instance, in the 

 cases of the alkaline salts and the ma^jnesian salt, neutralizing the com- 

 pounds thus obtained by means of cheap preparations of the respective 

 bases. The silicate of potass was manufactured at a glass-house by fusing 

 equal parts of pearl-ash and sand — a clear transparent glass, slightly deli- 

 quescent in the air-, was the result ; it was ground to powder under edge- 

 stones. 



