Little Falls, N. Y., filters at, 253. Loam in filters, 35. London, cost of operating filters at, 202. water-supply of, 255. Long, Prof., 131. Lorain, tests of mechanical filters, 161. Loss of head, 52. limit to, 60, 67. reasons for allowing high, 65. Louisville, mechanical filters at, 161. Magdeburg, filters at, 273. Maignen system, 181. Manchester, water-supply of, 275. Manganese, compounds of, as coagulants, 148. in ground-waters, 188. Massachusetts State Board of Health, see Lawrence Experiment Station. Mechanical filters, 159. application of, 199. efficiency of, 179. list of, 247. pressure filters, 180. rates of filtration used, 175. types of, 172. wasting effluent after washing, 163. Millford, Mass., filters at, 252. Mills, H. F., 97, 99, 102. Mount Vernon, N. Y., filters at, 252. Mud, see turbidity. Muddy waters, 113. Munich, water-supply of, from springs, 275. Nichols, Prof., suspended matters in European streams, 131. Nitrification, effect of, upon bacteria, 98. Odors, removal of, by filtration, 112. Organic matters in water, 83. removed by intermittent filters, 98. Paper manufacturing, filtration of water for, 5. Paris, ground-water supply of, 276. Palmer, Prof., 131. Passages through the sand in filters, 67. Pegan Brook, purification of, 110. Period, how computed and length of, 72. length of, dependent upon turbidity, 137. Piefke, 48, 50, 54, 63, 69, 73, 74, 75, 80, 84, 85, 90. Pittsburgh, experiments with mechanical filters, 162. Plägge and Proskauer, 84. Plymouth, Penn., typhoid fever at, 208. Pollution of European water-supplies, 93. Polluted waters, utilization of excessively, 111. Porcelain filters for household use, 183. Poughkeepsie, N. Y., filters at, 251. Pressure filters, 180. Providence, mechanical filters at, 159. Rate of filtration, 47, 224. at various places, 241. effect of, upon cost, 48. effect of, upon efficiency, 50. lower after scraping, 76. regulation of, 52. Red Bank, N. J., filters at, 193, 253. Regulation of filters, 52. old forms of regulators, 52. modern forms of regulators, 54. at Albany, 305, 308, 310. of mechanical filters, 178. Reincke, Dr., report on health of Hamburg for 1892, 226. Reinsch on the cause of poor filtration at Altona, 267. Reserve area required in case of ice, 18. Reservoirs, purposes served by, 133. Rock Island, Ill., filters at, 254. Roofs for filters, 16. Rotterdam, filters at, 272. St. Johnsbury, Vt., filters at, 251.