vi PREFACE 



interesting and practical subject, the author will feel that his labors 

 have not been in vain. 



It is coming to be recognized that agricultural bacteriology and, 

 agricultural chemistry are at many points intimately associated. 

 Hence, the writer has presupposed a knowledge of elementary 

 chemistry on the part of the student. However, most of the more 

 complex equations have been grouped in one chapter so they may 

 be used or omitted as the teacher sees fit. 



It has been more a question of what to exclude than what to 

 include. However, the writer has been guided throughout by the 

 needs of the student of agriculture, and hence where good, complete 

 volumes are available, as is the case with milk, water, sewage, and 

 some other subjects, a bare outline is given; so the student should 

 consult other works for a more exhaustive treatment. But in the 

 case of soils an effort has been made to go more into detail. Even 

 in these chapters, however, no attempt has been made to review all 

 of the literature. 



In the preparation of this work I have drawn freely from all 

 available sources. Much of the material was first written with a 

 complete reference to the literature, but it soon became apparent 

 that such a procedure would produce a work too large for the purpose 

 for which this was written. Hence, all references have been elimi- 

 nated. There are, however, listed at the end of most chapters a few 

 select works given in most cases because of the references which 

 they contain, and it is to these that the student is referred for 

 further details. At the end of the last chapter is given a list of 

 additional works which have been consulted in the preparation of 

 this book. 



To my friends and colleagues my hearty thanks are offered for 

 the valuable encouragement and assistance given in the preparation 

 of this book. I am under particular obligation to President E. G. 

 Peterson, Dr. F. S. Harris, Dr. B. L. Richards, Professors George 

 Stewart, C. T. Hirst, and E. G. Carter for reading parts or all 

 of the manuscript and offering many helpful suggestions, also to 

 Mrs. Blanche C. Pittman for her painstaking care in the preparation 

 of the manuscript for the press. 



J. E. G. 



LOGAN, UTAH, 1922. 



