PREFACE 



For several years courses of instruction have been 

 given at the University of Minnesota to classes of 

 young men who intend to become farmers and who 

 desire information that will be of assistance to them 

 in their profession. In giving this instruction mimeo- 

 graphed notes have been prepared, but the increase in 

 the number of students and the volume of notes have 

 necessitated the publication of this work. In its prep- 

 aration, it has been the arm> to? give, in condensed form, 

 the principles of chemistry which have a bearing upon 

 the conservation of soil fertility and the economic use 



of manures. 



Harry Snyder. 



University of Minnesota, 

 College of Agriculture, 



vSt. Anthony Park, Minn. 



April /$, iSgg. 



