66 ON THE CULTIVATION OF THE EARTH. 



" decompounded, are considered, in the present 

 " state of chemical knowledge, as elements. 



"The bodies incapable of decomposition at 

 " present known, are forty-seven ; ofthesej^lnrtj- 

 " eight are metals; six are inflammable bodies; 

 " and three substances, which unite with metals 

 " and inflammable bodies, ajid form with them 

 " acids, alkalies, earths, or other analogous com- 

 " pounds. 



" The chemical composition of plants has, 

 . " within the last ten years, been elucidated 

 " bv the experiments of a number of chemical 

 " philosophers, both in this and other countries ; 

 " and it forms a beautiful part of general che- 

 " mistry. If the organs of plants be submit- 

 " ted to chemical analysis, it is found that their 

 " almost infinite diversity of form, depends upon 

 " different arrangements and combinations of a 

 " very few elements ; seldom more than seven or 

 " eight belong to them, and three constitute the 

 " greatest part of their organised matter. 



" All the varieties of substances found in plants 

 " are produced from the sap, and the sap of plants 

 " is derived from water, or from the fluids in the 

 " soil, and it is altered by, or combined with, 

 " principles derived from the atmosphere." 



And again : " If any fresh vegetable matter, 

 " which contains sugar, mucilage, starch, or 

 " other -of the vegetable compounds solyble in 



