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ACKNOWLEDGMENTS 



The illustrations are by the author except No. 

 24, from Rollins and Linn, Lookout Mountain, 

 Tenn.; No. 78, from "Irrigation," by Newell; and 

 Nos. 80, 81, 83, and 84, which are from the Office 

 of Irrigation and Drainage Investigations, United 

 States Department of Agriculture. 



Perhaps the most valuable feature of the book is 

 the lists of crop rotations in the Appendix, which 

 were contributed by authorities on this subject in 

 the several states, as noted in connection with the 

 lists. These courtesies are gratefully acknowl- 

 edged. 



