" tion, the virtue is gone out of it. And as 

 " fenfible are we, by its reft, and lying to 

 " pafture, how, with its vigour, it renews alfo 

 ** its colour. We do not better fee and know 

 " when the plumb or grape is covered with, 

 or has loft, its bloomy hue, than we know 

 " by the colour the fertility of our foil : 

 " which colour arifes from the principles be- 

 fore intimated, of dung, air, fire, earth, 

 ' &c. mingled together; which, by often 

 " fowing, are abforbed into the corn in too 

 46 liberal a manner, to be renewed by a daily 

 ' recruit from thofe elements." 



This obfervation of Mr. Lifle's is agreeable 

 to what is faid above; that the fertility of 

 land is not any thing permanent in it, but is 

 fluctuating, fubject to be carried away by the 

 crops, and reftored to it again by the atmo- 

 fphere. Mr. Lifle attributes that partly to 

 dung ; but we mall fhew hereafter, that 

 thefe changes happen in land from the atmo- 

 fphere only, and where no dung or other ma- 

 nure is ufed. 



It is further obfervable, that land is enriched 

 by the atmofphere in proportion to the na- 

 ture and quality of the finer parts of it : for 

 all land is not equally enriched, though 

 equally expofed to the atmofphere. The 

 Iheer, (harp fands, in many places, appear to 

 be incapable of attracting or receiving the ve- 

 getable food ; for they continue barren for 

 ages, though conftantly expofed to the atmo- 

 fphere, 



