The filters, sedimentation-basin, and pure-water reservoir are connected in such a way as to make an exact separation of their costs impossible; but, approximately, the sedimentation-basin cost $60,000, the pure-water reservoir $9,000, and the filters $255,000. The sedimentation-basin thus cost $4,100 per million gallons capacity; and the filters complete cost $45,600 per acre of net filtering area, including all piping, office and laboratory building, but exclusive of land and engineering. ACKNOWLEDGMENT. The general plan and location of the plant were first conceived by the Superintendent of Water-works, George I. Bailey, M. Am. Soc. C. E., and the successful execution is largely due to his efforts. The members of the Water Board, and especially the Construction Committee, have followed the work in detail closely and personally, and their interest and support have been essential factors in the results accomplished. In the designs and specifications for the pure-water conduit the author is greatly indebted to Emil Kuichling, M. Am. Soc. C. E., and also for most valuable suggestions relative to the performance of this part of the work. To William Wheeler, M. Am. Soc. C. E., of Boston, the author is indebted for advice upon the vaulting and cross-sections of the walls, and these matters were submitted to him before the plans were put in final shape. All the architectural designs have been supplied by Mr. A. W. Fuller, of Albany. W. B. Fuller, M. Am. Soc. C. E., as Resident Engineer, has been in direct charge of the work, and its success is largely due to his interest in it and the close attention which he and the assistant engineers have given it. FOOTNOTES: [1] The American gallon is 231 cubic inches or 0.8333 of the imperial gallon. In this work American gallons are always used, and English quantities are stated in American, not imperial, gallons. [2] Filtration of River Waters. Van Nostrand & Co., 1869. [3] Annual Report of Albert F. Noyes, City Engineer for 1891. [4] Rept. Mass. State Board of Health, 1892, p. 541. See Appendix III. [5] The method of calculating the size is given in Appendix III. [6] A full table of frictions with various velocities and gravels was given in the Rept. of Mass. State Board of Health, 1892, p. 555. [7] Frühling, Handbuch der Ingenieurwissenschaften, II. Band, VI. Kapitel. [8] The American gallon is used throughout this book; the English gallon is one fifth larger. [9] Piefke, _Zeitschrift für Hygiene_, 1894, p. 177. [10] _Zeitschrift für Hygiene_, 1891, page 38. [11] _Journal für Gas- u. Wasserversorgung_, 1891, 208 and 228. [12] _Journal für Gas- u. Wasserversorgung_, 1893, 161.