PREFACE. 6701717 For a number of years the author has been looking for the appearance of a work on Sewerage which should embody the most recent data and ideas relating to the subject and treat of both the Combined and Separate Systems in a comprehensive manner, recognizing the fact that such a work is needed by city engineers and engineering schools. None such has appeared, and he has consequently undertaken the task of supplying the deficiency. No attempt has been made to treat at length the subject of Sewage Disposal, for the reasons stated in Chapter II. Parts II and III on the Construction and Maintenance of Sewers will, he believes, be appreciated by those who are called upon to superintend such work without previous experience, and even, he hopes, give valuable hints to many who are not novices; although he recognizes that the ground is by no means completely covered. For much of the matter therein contained he is indebted to the engineering periodicals, particularly the News and Record, but the greater part of it has never, to his knowledge, appeared in print. While primarily intended for practising engineers, the work has also been arranged with the idea that it may be useful as a text-book in engineering schools; Part I having already been so used by the author, and Part II having been largely given in the form of lectures to his classes. iii PREFACE TO THE THIRD EDITION. In response to many requests from instructors and city engineers for the addition to "Sewerage" of a more extended discussion of Sewage Disposal, this subject has been enlarged to fill four chapters of considerable length, in place of the twelve pages of the first edition. PREFACE TO THE FOURTH EDITION. THE author has taken advantage of the necessity for a fourth edition to still further increase the space devoted to Sewage Disposal, and to so revise the discussion of this subject as to bring it into accord with the latest conclusions of the recognized authorities. iv |