Agricultural Clieviistry. 315 



^ The question was to be solved : which of the cultivated plants 

 required ammonia in the manure, and which of them could do 

 without it. The manure was to give the means of raising, on 

 one and the same field, uninterruptedly and jet without ex- 

 haustion, the same crop, whether clover, wheat, or any other, 

 according to the wish or necessity of the farmer. 



I most readily admit that the idea of these manures could only 

 have arisen and taken root in the brain of a man of science^ 

 penetrated and inspired by the truth of his doctrines, but who had 

 before his mind's eye not the actual state of things, but an ideal 

 agriculture. It was folly to believe it even possible for a prac- 

 tical agriculturist to enter into these ideas, or to fancy that he 

 could, or would convert all his fields into experimental fields for 

 the sake of establishing fixed laws for agriculture ; it was folly 

 to call on others to enter on such an undertaking without any 

 prospect of being able to devote to it the time and energy which 

 were indispensable to its prosecution. 



The just punishment of my imprudence has overtaken me, 

 for I have been compelled to see that the very efforts I made 

 to give to agriculture a scientific foundation, have only had 

 the result of bringing agriculture into paths which, already 

 trodden for centuries, have led to no permanent improvement. 



In 1847 appeared (Journal, vol. viii. p. 226) the first paper 

 of Mr. Lawes on Agricultural Chemistry, in which he endea- 

 voured to prove, by the description of a series of facts, that 

 the manure for wheat, prepared by my prescription, had been 

 without effect, and was of no value to the fanner. He proceeded 

 without interruption from me for some years, during which I 

 was engaged in other investigations, till at last I found, to my 

 no small surprise, that, encouraged by my silence, he had suc- 

 ceeded in changing the scientific direction of agricultural re- 

 searches, and in bringing the subject back to the very point 

 where I had found it and taken it up in 1840. 



I had taught, that the food of plants consists entirely of inorganic 

 materials* 



That carbonic acid, ammonia, and water, are inorganic com- 

 pounds in the growth of plants : the hydrogen comes from the icater^ 

 the carbon from the carbonic acid, the nitrogen from the ammonia.'^ 



* 'Manual of Chemistry,' by Dr. Turner. Edited by Liebig and Gregory, 

 1842, p. Ml. 



f " Plants derive tlieir nouvishiiient exclusively from the mineral world. It is. 

 clear that i\vc first plants must liave done so ; and, although tlie decaying remains 

 of former pUiiits nmn coutril)ute to vegetation, we shall see that tliey do so under 

 mineral forms, axiA not essentially; tliey promote vegetation, but are not indis- 

 pensable to it. 



"The mineral food of plants, tlion, consists o{ curlionic acid, tnttcr, and ammonia, 

 all of which are obtained from tlie atin()sj)here ; and of siiiphui' i sulphuric acid),. 



