92 CATALYSIS, OR ACTION OF PRESENCE. 



tally different substance. The catalytic body, the 

 present body, the changing body itself, suffers no 

 change, except, perhaps, in some cases of ferments, 

 whose activity depends upon their being in a state 

 of decomposition, while the changed body loses 

 nothing of its substance. For example, starch is 

 converted into sugar by oil of vitriol. The acid 

 suffers no change. It acts by catalysis, and con- 

 verts the starch to sugar. So the peculiar principle 

 found near the eye of the potato, converts starch' 

 first into gum, called dextrine, and then converts 

 this into sugar of starch. So malt, by its gluten, 

 converts starch into sugar in the process of brewing 

 beer. But the effect of this action, may not be 

 confined to organic compounds only. It has lately 

 been extended, by an acute German chemist, to all 

 chemical changes ; and it has been maintained that 

 all chemical decomposition takes place in obedience 

 only to a third substance, acting by its presence. 

 Hence, this extension of the principle, will allow 

 the decomposition of the mineral elements of soil, to 

 be attributed to the catalytic action of the plant. 



138. Having considered the action of the organic 

 and inorganic elements of soil upon each other, it is 

 seen, that though great, this action would be but 

 very little, in centuries. The geine itself, would be 



