THIRD AMERICAN EDITION. ix 



the most careful examination of the chemical nature 

 both of the soil in which a given plant grows, and of 

 the plant itself, must be the foundation of all exact 

 and economical methods of cultivation. '* 



Of the importance of alkalies and salts to plants, 

 there would seem to be no doubt, and although the 

 credit of this discovery is in England given to Liebig, 

 it was not new in the United States, having been an- 

 nounced by Dr. S. L. Dana of Lowell, and urged 

 upon the attention of cultivators in the various Re- 

 ports on the Agriculture of Massachusetts, several 

 years ago. 



As in this work many chemical and technical terms 

 are necessarily made use of, and it may come into the 

 hands of some persons who are not familiar with them, 

 explanatory notes have been added which it is hoped 

 may render the text more intelligible. The notes 

 that are contained in the original work are distin- 

 guished by initials or abbreviations. 



A valuable addition has been made in the extracts 

 from the lectures delivered after the appearance of 

 Liebig's work by Professor Daubeny at Oxford, on 

 Agriculture and Rural Economy. The greater part 

 of the third lecture is given in the Appendix, being 

 a summary of the practical applications of the prin- 

 ciples developed and discussed in the body of this 

 work. 



It has been highly gratifying to the editor, to learn 

 from the gentleman under whose supervision the work 

 first appeared in England, that its republication, and 



