vi Preface 



to see something in the soil will have a better time at 

 farming, even if he makes no more money, than the man 

 who has not. 



I hope the student will carry out the experiments 

 given here as well as those given in my earlier Lessons on 

 Soil. The analytical methods are put in the Appendix 

 for the convenience of those who want them ; it is not 

 intended that all should be carried out by the student 

 but only such (if any) as may be desirable. I have 

 assumed no knowledge of chemistry: all the same the 

 student will need some chemical explanations, but these 

 must be supplied by the teacher. The vexed question of 

 how much pure chemistry is needed for an agricultural 

 course admits of no general answer: the teacher alone 

 can settle the matter for his own case and to him there- 

 fore the decision is left. 



To my colleague Dr Hutchinson I wish to tender my 

 best thanks for the care he has bestowed on the photo- 

 graphs for the book. 



E. J. Ri. 



rothamsted experimental station, 

 Harpenden. 



Octohtr 1915. 



