At Westerly, R. I., with a New York filter, the actual quantity of potash alum employed from Oct. 10, 1896, to March 1, 1897, was 1.94 grains per gallon, the amount being regulated to as low a figure as it was possible to use to secure satisfactory decolorization. There is no record of the color of the raw water. A very rough estimate would place it at 0.50 upon the platinum scale. The chemical employed in this case was alum, and two thirds as large a quantity of sulphate of alumina would probably have done corresponding work, had suitable apparatus for applying it been at hand. At Superior, Wisconsin, the water in the bay coming from the St. Louis River, having a color of 2.40 platinum scale, was treated experimentally with quantities of sulphate of alumina up to 4 grains per gallon, by Mr. R. S. Weston in January, 1899, but even this quantity of coagulant utterly failed to coagulate and decolorize it. At Greenwich, Conn., during 1898 the average amount of sulphate of alumina employed, as computed from quantities stated in the annual report of the Connecticut State Board of Health for 1898, was about 0.44 of a grain per gallon, and this quantity sufficed to reduce the color of the raw water from 0.40 to 0.30, platinum standard. This reduction is very slight, and it is obvious that this quantity of coagulant was not enough for decolorization. Some experiments bearing on color removal were made at East Providence, R. I., by Mr. E. B. Weston, and are described in the Proceedings of the American Society of Civil Engineers for September, 1899. In this case the color is reported to have been reduced from 0.58 to 0.10 platinum standard by the use of one grain of sulphate of alumina, containing 22 per cent of effective alumina, equivalent to about 1.30 grains of the ordinary article per gallon. The various experiments seem to indicate that a removal from 80 to 90 per cent of the color can be effected by the use of a quantity of sulphate of alumina equal to rather more than two grains per gallon for waters having colors of 1.00, platinum standard, and proportionate quantities for more and less deeply colored waters. With much less sulphate of alumina decolorization is not effected, and even larger quantities do not remove all of the color. The data are much less complete than could be desired, and it is to be hoped that experiments will be undertaken to throw more light upon this important subject. SUCCESSIVE APPLICATION OF COAGULANT.