vi AUTHOR'S PREFACE 



would be very markedly increased. It is equally true 

 that if all the lands on all the farms were properly 

 drained and given the chance to do their best, total yields 

 and total averages would be enormously augmented. 



These losses and the means of correcting them are 

 the theme of this text. In the preparation of the ma- 

 terial for the volume, an attempt has been made to put 

 into simple and concise terms the fundamentals of our 

 knowledge concerning the relation of water to agri- 

 culture, and of the relation of drainage to soil water. 

 The practical farmer has been in mind much more than 

 the engineer. Material has been introduced at the risk 

 of the charge of repetition, or even of the incorporation 

 of extraneous material, and for these reasons : 



1. That many persons who may use the work will 

 not have had a sufficient knowledge of these matters 

 to appreciate the importance of drainage in agricultural 

 practice. 



2. That many persons, including college men, who 

 may have taken courses in the physics of soils, will not 

 have sufficiently correlated the knowledge so acquired 

 to appreciate the inter-relations between the physical 

 conditions existing in soils, nor, consequently, the im- 

 portance of drainage in agricultural practice. 



3. The constituency is various. While designed spe- 

 cially as a text for students, it is hoped that the book 

 will find a place with the working farmer. 



Acknowledgments are due to various friends for in- 

 formation and suggestions in the preparation of the 

 manuscript. Acknowledgments are especially due to 

 Dr. George J. Bouyoucos and Charles H. Spurway, who 

 were at one time associated with the author in College 



work< JOSEPH A JEFFERY. 



DULUTH, MINN., 

 December, 1915. 



