324 Agriadtnral Chemistry. 



must remember that Messrs. Lawes and Gilbert ascribe the effect 

 of superphosphate of lime to the phosphoric acid, and that of 

 farm-yard manure to the organic constituents of the straw, and, as 

 we might expect from them, without their having ever made an 

 experiment with phosphoric acid alone, or with straiD alone. How 

 do they explain the effect of the clay and weed ashes, which gave 

 a heavier crop than the farm-yard manure, and one almost equal 

 to that yielded by the superphosphate? There can here be na 

 question of free phosphoric acid, nor of an excess of phosphoric 

 acid, nor even of an error of the press. The answer is (vol. viii. 

 p. 17) — " This is a curious result, and indicates that certain 

 mechanical as well as chemical conditions of soil are essential 

 to a favourable and healthy development of the organs of collec- 

 tion." 



To this experiment, the only one, of all made by them, which 

 deserved to be continued and more accurately studied, no farther 

 attention was paid. Possibly it might have happened that this 

 experiment might have led to the confirmation of the funda- 

 mental proposition of my doctrine. 



To the specimens of just reasoning given by Messrs, Lawes 

 and Gilbert, 1 shall add another, from a different quarter, which 

 is not less striking. 



Messrs. Chevaudier and Salvetat made, in 1852, certain re- 

 searches (' Ann. de Chim. et de Physique,' 3rd series, vol. xxxiv., 

 p. 307) in order to discover how it came to pass, that, of two 

 meadows, the one gave constantly a heavier crop of hay than the 

 other. Both were meadows of irrigation, but they received the 

 water from two different sources. One of these was called the 

 good spring {Ja bonne source), the other the bad spring [la mau- 

 vaisc source). That the great difference in the produce of the 

 two meadows depended on the fact that they were irrigated, one 

 with the good, the other with the bad spring, was a point on which 

 these two chemists had not a shadow of doubt. For the ma-- 

 jority of agricultural chemists, in all countries, resemble each 

 other in this, that they never entertain any doubt of the truth of 

 their opinions.* 



Without first trying whether the water of the good spring, if 

 used to irrigate the inferior meadow would increase its produce, 

 or whether the water of the bad spring applied to the better 

 meadow would diminish its produce ; without first deciding this 

 essential preliminary question, Messrs. Chevaudier and Salvetat 

 began, with an industry and perseverance which excite admira- 

 tion, to measure the water of the two springs employed to irrigate 



* Chemists -will think the style of Mr. Lawes very remarkable. The tone in 

 ■which he instructs me in purely chemical questions, is precisely that which a 

 schoolmaster adopts in dealing with a stupid, obstinate, and ill-mannered boy. 



