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ing loams or clay, which render its texture more 

 coherent and produdlive of vegetable nourifhment. 

 Among thefe may be reckoned marks of all kinds, 

 chalk, Ihells, and indeed every kind of fubftance, 

 which, merely by its texture, has the property of 

 rendering foils that are too adhefive, clofe, and heavy, 

 more light, open, and porous ; and thofe that are too 

 loofe and incoherent, more dcnfe, confident, and re- 

 tentive of whatever is added to it intentionally by 

 way of improvement, or liappens adventitioufly in 

 the courfe of nature. But marles, chalk, fhells, &c. 

 properly fpeaking, are improvers of the foil, not 

 merely as they correal and amend the texture, but 

 alfo by their chemical powers, which produce an in- 

 creafe of vegetable nourifhment, and give fertility to 

 the ground. So that they a6t in a double capacity, 

 that is to fay, both mechanically and chemically. 



It is perhaps of little ufe to enquire, whether the 

 above fubftances effentially contain any real vege- 

 table nourifhment, or only a6l minifterially in the 

 procurement and diftribution of the fame. All ab- 

 forbent fubflances are powerful attradlers of water, 

 oil, &c. and probably to the power of attradlion all 

 their virtue is owing. The humid vapours of the 

 air, which abound with putrid exhalations, are copi- 

 oufly imbibed by thofe abforbent earths, and from 

 thence are inhaled by the roots and fibred of plants. 



The 



