SECOND REPLY. 181 



that they must also be present in the proper proportion to 

 each other ; that regard to these proportions is of the 

 highest importance in reference to those plants which are 

 naturally inclined to produce varieties ; above all in refe- 

 rence to those plants, the chemical composition of which 

 renders them most liable to essential injury by alteration of 

 their constituents. All this especially concerns the Potato, 

 but does not much affect our grain, Rye and Wheat. 

 When we compare the constituents of the ashes of these 

 latter with the contents of a freshly manured soil, we find 

 the proportions of the two almost alike, and what is very 

 remarkable, when we abstract the constituents of the ash 

 of Rye from the contents of the soil, almost exactly that 

 proportion of the particular matters remains, that we find in 

 the ash of the Potato. The conclusion is therefore simple : 

 that we must in future never cultivate the Potato as the 

 first crop, as has generally been hitherto done throughout 

 the greater part of Europe, but we must begin with Rye, 

 and allow the Potato to follow it, or perhaps still better, 

 to come two years later, after Clover, if we would raise a 

 healthy produce, and in future be rid of the plague to 

 which we have recently been subject. The fundamental 

 proposition will henceforward stand firmly established, that 

 the nutrient matter which the plant itself takes up from 

 the soil, consists essentially only of the inorganic con- 

 stituents of the same, and that these, and not the organic 

 substances, constitute the peculiar richness of a soil. 



But the inorganic compounds are inseparably connected 

 with the organic in the plant, and if we would take pos- 

 session of the latter, we must receive the former into the 

 bargain. 



Yet they are not merely useless ballast, but substan- 

 ces essential to our bodies and their maintenance. Let 



