108 THE ART OF CULTURE. 



importance with that of agriculture, for to it belongs the produc- 

 tion of food for man and for animals ; on it depends the welfare 

 and development of the whole human species, the riches of states, 

 and all industry, manufacturing and commercial. There is no 

 profession in which the application of correct principles is pro- 

 ductive of more beneficial effects, or is of greater and more 

 decided influence. Hence it appears quite unaccountable, that 

 we may vainly search for one leading principle in the writings 

 of agriculturists and vegetable physiologists. 



The methods employed in the cultivation of land are different 

 in every country, and in every district ; and when we inquire 

 the causes of these differences, we receive the answer that they 

 depend upon circumstances. ( Les circonstances font les assole- 

 ments.) No answer could show ignorance more plainly. 



In addition to the general conditions, such as heat, light, mois- 

 ture, and the component parts of the atmosphere, all of which 

 are necessary for the growth of all plants, certain substances 

 are found to exercise a peculiar influence on their development. 

 These substances either are already contained in the soil, or are 

 supplied to it in the form of the matters known under the general 

 name of manure. But what does the soil contain, and what are 

 the components of the substances' used as a manure? Until 

 these points are satisfactorily determined, a rational system of 

 agriculture cannot exist. The power and knowledge of the 

 physiologist, of the agriculturist and chemist, must be united 

 for the complete solution of these questions; and, in order to 

 attain this end, a commencement must be made. 



The general object of agriculture is to produce in the most 

 advantageous manner certain qualities, or a maximum size, in 

 certain parts or organs of particular plants. Now, ' this object 

 can be attained only by the application of our knowledge of such 

 substances as we know to be indispensable to the development of 

 these parts or organs, or by supplying the conditions necessary 

 to the production of the qualities desired. 



The rules of a rational system of agriculture should enable 

 us, therefore, to give to each plant that which it specially requires 

 for the attainment of the object in view. 



The special object of agriculture is to obtain an abnormal 



