PAGE Fig. 1. Longitudinal Section of Yarrow Dam Site 10 2. Cross-Section of the Yarrow Dam 10 3. Plan of the Tabeaud Reservoir 17 4. Tabeaud Dam: Plan Showing Bed Rock Drains 18 5. Details of Drains 18 6. View of Drains 19 7. North Trench 20 8. South Trench 21 9. Main Central Drain 21 10. Embankment Work 23 11. Dimension Section 26 12. Cross and Longitudinal Sections 27 13. View of Dam Immediately After Completion 29 14. Cross-Section of Pilarcitos Dam 34 15. San Andres Dam 34 16. Ashti Tank Embankment 35 17. Typical New England Dam 40 18. Two Croton Valley Dams Showing Saturation 41 19. Studies of Board of Experts on the Original Earth Portion of the New Croton Dam 43 20. Studies of Jerome Park Reservoir Embankment 46 21 to 24. Experimental Dikes and Cylinder Employed in Studies for the North Dike of the Wachusett Reservoir 49 25. Cross-Section of Dike of Wachusett Reservoir 49 26. Working Cross-Section of Druid Lake Dam 53 27 to 29. Designs for the Bohio Dam, Panama Canal 55 30. Cross-Section of the Upper Pecos River Rock-Fill Dam 59 31. Developed Section of the San Leandro Dam 59 EARTH DAMS CHAPTER I. _Introductory._ The earth dam is probably the oldest type of dam in existence, antedating the Christian Era many hundreds of years. The literature upon this subject is voluminous, but much of it is inaccessible and far from satisfactory. No attempt will here be made to collate this literature or to give a history of the construction of earth dams, however interesting such an account might be. The object will rather be to present such a study as will make clear the application of the principles underlying the proper design and erection of this class of structures. In no way, therefore, will it assume the character or dignity of a technical treatise.