CLASSIFIED LIST OF 

 ILLUSTRATIONS 



PAGE 



1. "Plowing" Frontispiece 



2. Map of United States, normal annual precipitation. Fig. 41 ... . 137 



3. Map of western United States, irrigated and irrigable land. 



Fig. 72 227 



4. Map of United States, showing relative use of fertilizers. Fig. 



108 323 



5. Map of United States, sunshine received in different sections. 



Fig. 121 452 



6. Rock section. Granite. Fig. 1 8 



7. Rock section. Diorite. Fig. 2 10 



8. Rock section. Basalt. Fig. 3 11 



9. Rock section. Fossiliferous limestone. Fig. 4 12 



10. Rock section. Chert. Fig. 5 13 



11. Rock section. Sandstone. Fig. 6 13 



12. Photo-micrograph. Fine sand. Fig. 17 70 



13. Photo-micrograph. Silt. Fig. 18 71 



14. Influence of water film on soil granulation. Fig. 30 105 



15. Weathered Laramie sandstone. Fig. 7 15 



16. Types of weathering. Fig. 8 19 



17. Weathered limestone in quarry. Fig. 9 22 



18. "Pot-holes" in shale rock. Fig. 10 . . 25 



19. Lichen on granite rock. Fig. 11 28 



20. Tree roots spliting boulder. Fig. 12 29 



21. Section of residual soil from limestone. Fig. 13 38 



22. Section of muck underlain by marl. Fig. 14 42 



23. Section of sedimentary soil. Fig. 15 48 



24. Section of glacial soil. Fig. 16 58 



25. Proportion of separates in sandy soil. Fig. 21 75 



26. Proportion of separates in silt soil. Fig. 22 75 



27. Proportion of separates in clay soil. Fig. 23 76 



28. Undesirable soil structure. Fig. 27 90 



29. Ideal soil structure. Fig. 28 91 



30. Excessive checking of clay soil. Fig. 29 99 



31. Ice crystals in field soil. Fig. 31 108 



32. Honey-comb ice crystals. Fig. 32 109 



(xxv) 



