PREFACE xi 



regions, might profitably organize classes in this subject. 

 Classes in fertilizers and related subjects are taught as 

 a matter of course, but the water factor, of greater impor- 

 tance, is given incidental mention in courses on soils or 

 plant physiology. At the Utah Agricultural College it has 

 been found satisfactory to give a half-year course in dry- 

 farming, followed by a half-year course in irrigation 

 practice, the two courses constituting a year's study of 

 the water factor in agriculture. 



The irrigation literature of the world has been quite 

 fully examined in the preparation of this book; but, since 

 the work has been done far from large libraries, many 

 important papers have been inaccessible. However, as a 

 possible compensating condition, the work has been done 

 within hearing of the ripple of the irrigation ditch, in 

 the heart of the irrigated section. Free use has been made 

 of all available information, but of especial help have 

 been the magnificent series of irrigation bulletins issued 

 by the Irrigation Investigations of the Office of Experi- 

 ment Stations of the United States Department of Agri- 

 culture. The splendid work of the Bureau of Soils of the 

 United States Department of Agriculture has also been 

 of the greatest assistance. It is a pity that the heated dis- 

 cussion of a theory should overshadow this vast, accurate 

 and remarkable soil work, the like of which, issuing from 

 one institution, is not to be found. 



At the end of each chapter has been placed a short 

 list of references for the use of those who desire to carry 

 their studies further. Care has been taken, except in 

 two or three instances, to suggest only such materials as 

 are readily available. These references would make a 

 very good working library on irrigation and may be 

 obtained at a slight cost. In Appendix C is given a brief 



