138 THE ART OF CULTURE. 



The development of the stem,, leaves, blossoms,, 

 and fruit of plants is dependent on certain condi- 

 tions,, the knowledge of which enables us to exer- 

 cise some influence on their internal constituents as 

 well as on their size. It is the duty of the natural 

 philosopher to discover what these conditions are; for 

 the fundamental principles of agriculture must be 

 based on a knowledge of them. There is no pro- 

 fession which can be compared in importance with 

 that of agriculture, for to it belongs the production 

 of food for man and animals ; on it depends the wel- 

 fare and development of the whole human species., 

 the riches of states, and all commerce. There is no 

 other profession in which the application of correct 

 principle is productive 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 cir- 

 cumstances. (Les circonstances font les assolemens.) 

 No answer could show ignorance more plainly, 

 since no one has ever yet devoted himself to ascer- 

 tain what these circumstances are. Thus also when 

 we inquire in what manner manure acts, we are 

 answered by the most intelligent men, that its 

 action is covered by the veil of Isis ; and when we 



