62 ON THE CULTIVATION OF THE EARTH. 



food to vegetables, and the influence of lodging 

 and climate on them, is not so generally imder- 

 stood ; yet it is equally necessary it should be, 

 as it is this alone which can enable a person to 

 follow cultivation successfully. 



It has been demonstrated by direct experiment, 

 and is admitted by all philosophers, that earth 

 alone, in any combination of its primitive or sim- 

 ple principles, is incapable of maintaining plants 

 in health, or to enable them to attain maturity ; 

 that vegetables require food to sustain them ; 

 that their food consists of animal and vegetable 

 matter, reduced by decomposition, to a soluble 

 state ; and that such food can only be taken up 

 or consumed by plants, in a state of liquid, 

 through its roots ; but of what peculiar ele- 

 ments or principles such food is composed oti 

 by what means prepared, or how the requisite 

 proportion of the liquifying medium is detei'- 

 mined; or by what peculiar powers such food 

 is taken up by vegetables, and digested, and 

 appropriated to their various increase and pro- 

 ductions, are as yet subjects of discussion and 

 uncertainty. 



To establish these points, it has been found 

 necessary to discover and investigate the ele- 

 raentaiy principles of which vegetables and ani- 

 mals are composed ; and also to ascertain bv 

 what organic powers the process of vegetation is 



6* 



