8 PREFACE 



Although written primarily for use as a text book, it is 

 hoped that this volume will be of interest to those engaged 

 in practical agriculture. 



Many of the illustrations were made from photographs 

 secured from the files of the Iowa State College. In addi- 

 tion, the trade literature of the following manufacturers 

 was drawn upon : 



International Harvester Company of America; John 

 Deere Plow Co. of Moline, 111.; Moline Plow Co.; W. & L. 

 E. Gurley; Eugene Dietzen Co.; Keuffel and Esser Co.; 

 Parlin and Orendorff Co. ; Fairbanks, Morse and Co. ; Hayes 

 Pump and Planter Co. ; Hunt, Helm, Ferris & Co. ; J. D. Tower 

 and Sons Co.; Western Wheeled Scraper Co.; Pattee Plow 

 Co.; Avery Company; Emerson-Brantingham Co.; M. 

 Rumely Co. ; American Seeding Machine Co. ; Oliver Chilled 

 Plow Works; Hart-Parr Co.; Red Jacket Mfg. Co.; A. Y. 

 McDonald Mfg. Co.; Louden Machinery Co.; Gale Mfg. Co.; 

 Sandwich Mfg. Co.; Aspenwall Mfg. Co.; Wilder-Strong 

 Implement Co. ; Port Huron Engine and Thresher Co. ; J. L. 

 Owens Co.; Charles A. Stickney Co.; Twin City Separator 

 Co.; Cushman Motor Works; F. E. Meyers & Bro.; D. M. 

 Sechler Carriage and Implement Co.; Roderick Lean Mfg. 

 Co.; Janesville Machine Co.; LaCrosse Plow Co.; The John 

 Lanson Mfg. Co.; J. I. Case Plow Works; J. I. Case Thresh- 

 ing Machine Co. ; Johnson & Field Mfg. Co. ; Racine Sattley 

 Co. ; Kewanee Water Supply Co. ; and others. 



Valuable assistance was secured from Mr. M. F. P. 

 Costelloe, Associate Professor of Agricultural Engineering, 

 Iowa State College, who read the manuscript for Parts I to 

 IV, inclusive. Mr. J. H. Weir, the Editor, did very efficient 

 work on the manuscript, which is appreciated. 



Ames, Iowa. J. B. DAVIDSON. 



February, 1913. 



