Vi PREFACE TO THE 



in the art of agriculture, induced the editor to suggest 

 its republication in this country. 



Contrary to the expectations of the author, and of 

 the editor, the work has received the attention not 

 only of scientific readers, for whom it was written, 

 but of practical agriculturists, andlthose who could 

 hardly have been supposed prepared to derive much 

 advantage from its perusal. The influence of the 

 opinions of Professor Liebig, and the impetus the 

 appearance of the present work gave to the advance- 

 ment of scientific agriculture, have been evinced by the 

 many publications which have since appeared, both in 

 Great Britain and in this country. 



What is valuable in too many of these publications, 

 diluted as it has been and mingled with erroneous 

 statements, was for the first time given in a consistent 

 shape in the present work. 



Although the fact that nitrogen is essential to the 

 nutrition of plants was known before the publication 

 of Professor Liebig's work, and it had, indeed, been 

 ascertained by Saussure, that germinating seeds absorb 

 nitrogen, it was not supposed that it is derived from 

 the atmosphere exclusively. And this has been 

 deemed the chief discovery of the author, so far as 

 practical questions are concerned. It had indeed been 

 suspected, that very small quantities of ammonia in 

 the atmosphere might furnish the nitrogen, ammonia 

 being a compound of nitrogen and hydrogen. It 

 may be objected, that the quantity of ammonia pres- 

 ent in the atmosphere, and in rain and snow water, is 



