On Agricultural Chemistry. 



227 



and have the means, will not freely embark their money on 

 the improvement of their farms, for want of that knowledge 

 which would enable them to calculate their returns with any de- 

 gree of certainty. Hence, too, the tenant farmer is frequently 

 compelled to adopt a rotation of crops entirely prejudicial to his 

 interest, retained only because it happened to be the custom of 

 our ancestors a century ago, while the same rotation is enforced 

 upon the farmer who expends 8Z. an acre on his land, as upon 

 him who expends only 3/. 



Liebig's work on Agricultural Chemistry, published in the 

 year 1840, attracted very generally the attention of British agri- 

 culturists. In those pages they were first made acquainted with 

 the important aid they were likely to obtain from the science of 

 chemistry applied to the cultivation of the soil. The work of 

 Sir Humphry Davy upon the same subject can hardly be said to 

 have influenced the practice of agriculture. He applied the 

 knowledge of chemistry, as it then existed, with his usual sagacity, 

 but at the period in which he wrote organic chemistry was quite 

 in its infancy. The labours of the German and French chemists 

 during the last thirty years have principally been directed to the 

 study of organic chemistry which owes its present important 

 position to the number of accurate analyses they have given to the 

 world. It is much to be regretted that Liebig should have 

 altered, in the third edition of his work, so many of the views and 

 opinions laid down in the first ; or that a hasty visit to England, 

 during which (as he says in his preface) he made himself ac- 

 quainted with practical agriculture, should have caused him to 

 pronounce as valueless the experiments of Boussingault, whose 

 opinions are entitled to respect, as coming from one in whom 

 are combined the scientific chemist and the practical farmer. 

 Without entering into the merits of the different opinions main- 

 tained by these distinguished chemists, I may here observe that 

 many of the errors into which Liebig has fallen, have, I think, 

 arisen from his not sufficiently considering what agriculture really 

 is. Practical agriculture consists in the artificial accumulation of 

 certain constituents to he employed either as food for mem or other 

 animals, upon a space of ground incapable of supporting them in its 

 natural state. This definition of agriculture is, I think, import- 

 ant, as distinguishing English agriculture at least from the system 

 pursued in various parts of the world, where the population is 

 small and the land of little value, viz. of taking only the natural 

 produce of the soil, without any effort to increase it, and in time 

 abandoning it for a soil as yet undisturbed. If Liebig had suffi- 

 ciently considered this distinction, he would not have assumed 

 that certain substances employed as manures are of little value, 

 because plants and trees, in their natural state, are capable of 



