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analyzed, they will be found to contain a large proportion of 

 •water and charcoal ; alfo fat and effential oils, refins, gums, 

 and vegetable acids, all of which are reducible to water, pure 

 air, inflammable air and charcoal ; a fmall proportion of fixed 

 alkali is alfo found, fome neutral falts, moft commonly 8;ypfum, 

 tartar vitriolate, common fait, and fait of fylvius. In corn, and 

 particularly wheat, phofphorated felenite is alfo found. 



Hence we fee that, on the laft analyfis, the only "fubftance, 

 common to the growing vegetables, and the foils in which they 

 grow, are water, coal, different earths, and falts : Thefe, 

 therefore, are the true food of vegetables ; to them we fliould 

 alfo add fixed air, though by reafon of its decompofition it may 

 not be diftindly found in them, or at leaft not diftinguifhable 

 from that newly found during their decompofition. 



I SHALL now examine the feparate fundtions of each of thefe 

 ingredients. 



Of Water. 



The agency of water in the procefs of vegetation has never 

 been doubted, though the manner in which it contributes to 

 it has not, until of late, been diftinftly perceived. Dodor 

 Hales has fhewn that in the fummer months a fun-flower, 

 weighing three pounds avoirdupoize, and regularly watered 

 every day, paflTed through it or perfpired 22 ozs. each day, 

 that is, nearly -^ its weight. He alfo found that a cabbage 

 plant, weighing i lb. 9 ozs. fometimes perfpired i lb. 3 ozs. 



but 



