124 ON FALLOW. 



tility for the same plant, and to make it fit for the cultivation of 

 one, two, or for all plants ? 



The latter questions are proposed by the art of Agri- 

 culture ; but they are not susceptible of solution by means of 

 the art. 



When a farmer institutes experiments for the purpose of mak- 

 ing a field fertile for plants which it would not formerly bear, 

 the prospect of success must be small, unless he is guided by 

 scientific principles. Thousands of farmers try analogous expe- 

 riments in various ways, and the results of these constitute a 

 mass of experience, out of which a method of culture is finally 

 formed ; and this method suffices for a certain district. But the 

 same method fails with a neighboring district, or it may prove 

 actually injurious. 



What an immense amount of capital and power is lost in such 

 experiments as these ! What a very different and much more 

 certain path does Science follow ! It does not put us in danger 

 of failure, and it gives us the best security of success. 



If the causes of failure or the causes of sterility of a soil for 

 one, two, or three plants be ascertained, the means of obviating 

 the sterility follow as a matter of course. 



The methods of cultivating soils vary with their geological 

 characters. In basalt, grauwacke, porphyry, sandstone, lime- 

 stone, &c, let us suppose that there are present, in different 

 proportions, certain chemical compounds essential to the growth 

 of plants, and which must therefore exist in fertile soils; then 

 we are able to explain in a very simple manner the difference 

 in the methods of culture ; for it is obvious that the soils formed 

 by the disintegration of the above rocks must vary in the pro- 

 portion of their essential constituents, just as the rocks themselves 

 vary. 



Wheat, clover, and turnips, require certain constituents from 

 the soil ; and hence they cannot flourish in a soil from which 

 these are absent. Science enables us to recognise these neces- 

 sary constituents, by the analysis of the ashes of the plants ; and 

 if we discover the absence of these ingredients from the soil, the 

 cause of its sterility is obvious. 



