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reft, especially if the ploughings arc not very fre- 

 quently repeated before the feed is fown. 



The famous Mr. Tull, indeed, carried his idea 

 of the advantage of repeated ploughings to fuch a 

 height, as to fuppofe they would fupply the place 

 of manure entirely. This was doubtlefs an error; 

 but an error which men are very liable to fall into 

 from their warmth in fupporting a favourite hy- 

 pothecs. Repeated ploughings, however, are an 

 excellent method of rendering land fweet and fer- 

 tile, by deilroying the weeds, and expofing all its 

 parts to the kindly influence of the fun and air, by 

 which means it attracts a larger quantity of falts, 

 and is better pulverized. 



If we examine tracts of land which have not 

 been cultivated, we find nature has adapted dif- 

 ferent kinds of plants to moft of the diftingui fri- 

 able varieties of foils; and although fome be- 

 longing to one, may from fome caufe or other be 

 found on lands of a different quahty, they fel- 

 dom thrive, or perfect their feeds, fo as to become 

 general. 



Mr. Ti/ll thinks that the only difference in 

 foils, except their richnefs, is occaiioned by the 

 diiferent degrees of heat and moifture that they 



O 3 receive j 



