PREFACE. ix 



have been relegated to the Appendices attached to 

 each chapter. 



The author's somewhat wide experience as a Uni- 

 versity Extension Lecturer, and as a Lecturer in con- 

 nection with County Council schemes of agricultural 

 education, during the last few years, induces him to 

 believe that the work may be of especial value to 

 those engaged in teaching agricultural science. 



He has to express the deep obligation he is under, 

 in common with all writers on Agricultural Chemis- 

 try, to the classic researches of Sir John Bennet 

 Lawes, Bart., and Sir J. Henry Gilbert, now in pro- 

 gress for more than fifty years at Sir John Lawes' 

 Experiment Station at Eothamsted. His debt of 

 gratitude to these distinguished investigators has 

 been still further increased by their kindness in per- 

 mitting him to dedicate the work to them, and for 

 having been good enough to read portions of the work 

 in proof. In addition to the free use which has been 

 made throughout the book of the results of these 

 experiments, the last chapter contains, in a tabular 

 form, a short epitome of some of the more important 

 Eothamsted researches on the action of different 

 manures. 



To the numerous German and French works on the 

 subject, more especially to Professor Heiden's encyclo- 

 paedic 'Lehrbuch der Dlingerlehre' and the various 

 writings of Dr Emil von Wolff, the author is further 

 much indebted. 



