10 QUARTERLYJOURNAL. 



founded on a knowledge of the articles of food required by plants 

 in general, and by each particular kind of plants. 



Until a few years ago, the knowledge possessed on this point 

 was so defective, that it furnished no certain basis for any system 

 of agriculture, and all scientific farming was looked on with great 

 distrust. It was considered safer to trust to a certain routine of 

 practice which was found to work well in many cases, but the rea- 

 son of which was unknown, than to have recourse to scientific 

 principles which, however plausible they might seem, rarely led 

 to any profitable application. But practices foimded on blind rou- 

 tine must in many cases be misapplied, and the art pursued un- 

 der such a system must remain stationary. Of the imperfection 

 of the art of agriculture it is unnecessary to speak, and as to its 

 improvement it may be affirmed with great truth that while all the 

 other mechanical arts have been making such wonderful progress, 

 this one, which occupies more men than all the rest together, has 

 scarcely partaken of the movement, and that with the exception of 

 some improvements of its instruments, for which it is indebted to 

 other arts, it is now, in all essential respects, at the same point it 

 was two thousand years ago. 



Agriculture is however destined no longer to remain stationary. 

 Recent improvements in organic chemistry are changing the whole 

 aspect of vegetable and animal physiology, and rendering these 

 sciences susceptible of practical application. The mode in which 

 plants are supplied with food, and the kind of food they require, 

 are becoming better understood, and the theory of manures is be- 

 coming more perfect ; in a word, a science is springing up which 

 will revolutionize the whole art of agriculture, and enable it to 

 take its rank among the mechanical arts founded on fixed scientific 

 principles. In a few years it will be considered as absurd for a 

 man to undertake the management of a farm without having ac- 

 quired a theoretical knowledge of agriculture as it would be to at- 

 tempt to practice engineering without a knowledge of geometry. 



In this paper, I propose to point out in as plain a manner as 

 may be, what are the materials out of M-hieh the substance of 

 plants is formed and the sources whence these materials are de- 

 rived, and thus explain the action of various substances used as 

 manures. I have nothing new to add to what is contained in the 

 treatises of Liebig, Dumas and others, on this subject ; I only hope 



