28. Y-branch of vitrified tile pipe 64 29. Eighth bend of vitrified tile pipe 64 30. Sub-surface tiling 65 31. Photograph of tile laid as if for sewage disposal 66 32. Sub-surface tiling with broken stone or gravel 67 surrounding pipe 33. Sub-surface systems on irregular ground 68 34. Special casting of double Y-branch with swinging 69 gate 35. Double Y-branch with valves on branches of main 70 carrier 36. Sub-surface tiling system with underdrains 71 37. View of sand-filter beds for village in 75 Massachusetts 38. Layout for intermittent sand filtration 78 39. Intermittent sand-filtration beds 79 40. Portion of distributing troughs for sand filters 80 41. General view of disposal plant at Bedford 81 Reformatory 42. View of sand filter with distribution trough. 82 Settling tank is at the end of the bed 43. View of diverting manhole 83 44. Plan of diverting manhole 84 45. Five-way diverting manhole 85 46. General plans of contact-bed system near Albany, 89 N. Y., opposite page 47. View of sprinkling filter at Dansville, Pa., in 95 winter 48. Distribution of sewage and arrangement of check 106 levees on a hillside 49. Distribution of sewage on a hillside of moderate 107 slope 50. Square beds for orchards according to some 108 Western practice 51. Grain-field in spring in process of irrigation 109 PRACTICAL METHODS OF SEWAGE DISPOSAL FOR RESIDENCES, HOTELS AND INSTITUTIONS CHAPTER I INTRODUCTORY