[63] In the _Centralblatt für Bakteriologie_, 1895, page 881, Reinsch discusses at length the cause of the inferior results at Altona in winter, and has apparently discovered a new factor in producing them. Owing to defective construction of the outlets for the sedimentation-basins they have failed to act properly in presence of excessive quantities of ice, and the sediment from the basins has been discharged in large quantity upon the filters, and a small fraction of the many millions of bacteria in it have passed through the filters. He has experimented with this sediment applied to small filters, and has become convinced that to secure good work under all conditions a much deeper layer of sand than that generally considered necessary must be used, and his work emphasizes the importance of the action of the sand in distinction from the action of the sediment layer, which has often been thought to be the sole, or at least the principal, requirement of good filtration. [64] Licht- u. Wasserwerke, Zürich, 1892, page 32. [65] Descriptions of some of the leading European ground-water supplies were given by the author in the Jour. Asso. Eng. Soc., Feb. 1895, p. 113. [66] “_Arbeiten aus dem Kaiserlichen Gesundheitsamte_,” vol. xiv. p. 260. INDEX. Albany, N. Y., filters at, 254, 288. Alkalinity, 155. Altona, double filtration at, 198. filters at, 265. Alum, use of, in filtration, 92, 144. American cities, water-supplies of, and typhoid fever in, 211. Amsterdam, filters at, 272. iron removal at, 192. Anderson process, 147. Antwerp, filters at, 272. Asbestos as filtering material, 181. Asbury Park, iron removal at, 192. Ashland, Wis., filters at, 252. Area of filters to be provided, 47. Bacteria, apparent and actual removal of, by filters, 87. from underdrains, 87. in Elbe at Altona, 228. in fæces, 215. in water, 84. number to be allowed in filtered water, 222. of cholera in river water, 231. of typhoid fever, life of, in water, 216. of special kinds to test efficiency of filtration, 86. to be determined daily, 222. Bacterial examination of water, 93. Berlin, regulation of depth of water, 59. cholera infantum from water, 229. friction in underdrains, 44. regulation of rate, 53, 55. water works, 261. Berwyn, Penn., filters at, 253. Boston, protection of purity of water-supply, 110. experimental filters at, 73. Bremen, double filtration at, 198. Breslau, filters at, 274. Brussels, ground-water, supply of, 276. Budapest, filters at, 274. Burton, regulation of rate at Tokyo, Japan, 58. Carpenter, Prof. L. G., 24. Chemnitz, intermittent filtration at, 107. Chicago, reduced death-rate with new intake, 217.