PREFACE 



THIS book is written for three purposes: first, as a text-book 

 0^ for agricultural students ; second, as a reference book for the prac- 

 ^ tical farmer; and, third, as an aid to the land owner who desires 

 ij information in the personal management of his land. 



Soil physics is the application of physics to soils. It is so 

 ^ closely related to other sciences that it becomes necessary to trespass 

 upon the ground of some of them, notably botany, geology, chem- 

 istry, and zoology, to present certain subjects clearly and com- 

 pletely. Soil physics dovetails in with the closely-related phases 

 of agronomy, as soil biology, soil fertility, crop production, and 

 agricultural engineering, to such an extent that it is necessary to 

 give material very closely related to all of these. 



An attempt has been made to emphasize the principles of soil 

 hysics, omitting the details of practice except where necessary for 

 purposes of illustration. Although the book is written in the Middle 

 West, yet the principles given apply anywhere. 

 The arrangement of the matter presented has been carefully 

 \$ planned from the teaching standpoint, and has been tested in the 

 VL classroom for several years. 



^*^ Various sources of information have been used by tlie authors 

 and acknowledgment made accordingly. 



,T. (i. MOSIKH, 



A. F. (lUSTAFSOX. 

 College of Agriculture, 

 University of Illinois, 

 Urbana, 111., October, 1!)17. 



