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under cultivation, this upper ftratum will be pro- 

 portionably increafed by the more frequent addi- 

 tion of manure, and the roots and items of the 

 plants that grow in and upon the fame; and 

 therefore, as was faid, conftant culture improves 

 and not impovcrifhes land, as its fertility is gene- 

 rally, perhaps it may with truth be faid always, 

 in proportion to the depth of this adventitious 

 ltratum; for it is by no means an original or pri- 

 mitive earth, but a combination of vegetable and 

 animal matter, or of one of them feparately, pro- 

 duced by putrefaction and diflblution, which being 

 by culture intimately blended with the original 

 foil, perhaps fand, or gravel, &x. of themfelves 

 barren, a fertile foil is at length procured with 

 increafing powers, as cultivation is multiplied 

 and extended. 



The practice of the kitchen gardeners, near the 

 metropolis, and in the vicinity of mod market 

 towns, will at once illuftrate and confirm the 

 doctrine here advanced. They frequently raife 

 three or four crops annually on the fame ground, 

 and fupport fuch an extraordinary cxhauftion 

 folely by culture and manure. The rent of their 

 land is too high to admit of fallowing, and the 

 goodnefs of their crops plainly fhews it does not 

 Hand in need of it. Labour and dung anfwer 



D 2 every 



