Principles of Part II. 



years longer fruitful than the other part of 

 the iheep-fbld. 



THIS chief inftrument, then, that nature 

 makes ufe of to enrich the earth, is the air. 

 Even the richeft foils require its continual 

 influence. On what principles of the air 

 this fructifying quality depends, we cannot 

 inquire, until we have afcertained the na- 

 ture of the different manures which feem 

 to operate by attracting thofe principles 

 from the air. The flrong and lafting vege- 

 tative power which the air communicates 

 to the earth, mould teach us to make a 

 greater ufe of its influence than what we 

 do. Why mould we not raife the whole 

 furface into fold-dikes ? Other manures do 

 not operate till the fecond or third year 

 after they are laid on ; this operates imme- 

 diately. A farmer cannot, at a medium, 

 dung an acre under _$/; this might be 

 done for 30*. Dung fills the ground with 

 weeds; this method cleans it. Manures 

 cannot be found every where 5 this practice 



may 



