PREFACE Vll 



used for the larger purpose of establishing a scientific pro- 

 cedure in the affairs of life. 



The author desires to express his deep appreciation of the 

 helpful suggestions and criticisms of those who have read 

 the manuscript for this text, or portions of it. Special 

 acknowledgments are due Dr. R. J. Pool of the Department 

 of Botany; Professor H. C. Filley of the Department of 

 Farm Management; Professor Alice M. Loomis of the 

 Department of Home Economics; Professor George E. Love- 

 land, Director of the U. S. Weather Bureau; Professor G. D. 

 Swezey of the Department of Astronomy; and Dr. R. A. 

 Lyman of the Department of Physiology, all of the Univer- 

 sity of Nebraska, together with Professor B.C. Hendricks of 

 the Department of Physics in the State Normal School at 

 Peru, Nebraska. He is under special obligation to Professor 

 A. E. Sheldon, Lecturer on Political History and Secretary 

 of the State Historical Society, and to Mrs. Sheldon, for 

 their very helpful criticisms in their readings of the manu- 

 script. The author assumes, however, all responsibility 

 for errors that may have crept into the text. 



Aside from acknowledgments made in connection with 

 single illustrations, the author wishes to express his apprecia- 

 tion for other illustrations from : 



U. S. Forest Service, Figs. 37 40, 76, 83, 84, 86, 88. 



U. S. Weather Bureau, Figs. 32, 48, 102. 



U. S. Public Health Service, Figs. 15, 21, 25. 



U. S. Public Roads and Engineering, Figs. 29, 69. 



U. S. Reclamation Service, Figs. 38, 39. 



U. S. Geological Survey, Figs. 92, 112. 



Division of Publications, U. S. Department of Agriculture, 

 18, 24, 26, 27 28, 36, 47, 67 68, 73, 75, 77, 79, 80, 81, 82, 85, 93, 

 95> 96, 97, 98, 103, 104, 105, 106, 107, 108, in. 



