OF ARTIFICIAL MANURES. 157 



composition of water, and all that is wanting is sim- 

 ply a method of rapidly and cheaply decomposing 

 this fluid. That, again, we may advance so far as to 

 manure our fields with air will no longer seem in- 

 credible, when it is considered that four fifths of the 

 atmosphere are made up of nitrogen, and that this 

 nitrogen, if it can be compelled to combine with hy- 

 drogen to form ammonia (or with oxygen to form 

 nitric acid), will assuredly prove as good a manure 

 as the ammonia in guano, in drainings, etc. On a 

 small scale and by a somewhat complicated process 

 this is already possible ; why, then, may we not at- 

 tain to the solution of this problem in a simpler 

 method, and turn it to practical account on a scale 

 of greater magnitude ? If an actual necessity only 

 once exists, science will disclose the way, and experi- 

 ence make it a practicable means of satisfying that 

 want. 



The inquiries relative to artificial manures which 

 chemistry has to answer, are identical with those that 

 were formerly proposed when treating of natural ma- 

 nures. 



1. How do these manures produce their effect? 

 For what kind of soil and for what kind of crops are 

 they especially adapted? This is learned by reducing 

 them accurately into their separate constituents, and 

 by subsequently comparing these constituents with 

 those of the plants to which they are proposed to be 

 applied as fertilizing agents. For an absolutely cer- 

 tain conclusion, an examination of the soil is indeed 

 14 



