HOWSON AND HOWSON COUNSELLORS AT LAW SOLICITORS OF PATENTS PHILADELPHIA Forrest Building, 119 South Fourth Street NEW YORK Potter Building, 38 Park Row WASHINGTON Atlantic Building, 928 F Street TESTING MACHINES AND HYDRAULIC PRESSES. We are always prepared to make tests of all kinds. TINIUS OLSEN & CO. 500 NORTH TWELFTH STREET, PHILADELPHIA, PA. KEYSTONE ENGINE AND MACHINE WORKS, WILLIAM L. SIMPSON, Manufacturer of Engines, Boilers, Pumps, Heaters, Etc. Engines and Power Indicated. Special attention given to Repairing Automatic and other Engines. Cylinders Bored Out in Position by Special Machinery. Sales Agent for The Buckeye Automatic Cut-Off Engines. Office, FIFTH and BUTTONWOOD STS., PHILADELPHIA TELEPHONE 1891. THE Franklin Institute is not responsible for the statements and opinions advanced by contributors to the Journal. THE COLOR OF WATER. BY DESMOND FITZGERALD AND WILLIAM E. Foss. As many cities and towns are obliged to depend upon surface waters for their supplies, and as surface waters are liable to be discolored by the vegetable matter with which they come in contact, making them objectionable in appearance, it is important to have an accurate scale with which to measure the amount of the discoloration. For several years past, this matter has received much attention upon the Boston Water Works. One of the principal sources supplying the city of Boston is that of the Sudbury River. The area of the water-shed above the point of taking, is about seventy-four square miles. On this area several large storage reservoirs have been built for the purpose of equalizing the yield of the streams. As the sites of the reservoirs have been mostly stripped of all organic matter, the effect of storage is to reduce the color of the water delivered by the feeders, but as it is impracticable to keep VOL. CXXXVIII. 26 the water in store long enough to decolorize it completely, much study has been given to the source and amount of the color delivered by the streams supplying the reservoirs. It has been found, as was expected, that the swamps and meadows were the principal sources of color. In July, the color of the water coming from the swamps is a rich reddish-brown, and in the autumn, after the leaves have fallen, the color has more of a greenish cast. The color of the brooks varies constantly during the year, depending largely upon conditions which cannot be now discussed. In winter the color is naturally low. In the spring the color is high, reaching its maximum in June, and a second maximum occurs in December. In making plans for the improvement and drainage of the swamps it became important to be sure of the measurement of the colors, and as the color of the Boston water is almost an exact gauge of the organic matter which it contains, it also became important that the color of the water delivered to the consumers should be readily and accurately measured on some correct scale. It is the purpose of the writers of this article to consider here the matter of scale and methods of comparison. When solar light is transmitted through a water containing foreign matter, some of its components are wholly or partially absorbed and the transmitted light is more or less colored in consequence. The color depends on the nature of the missing rays, or is the resultant of the rays which have been transmitted. The greater the depth of the water through which the light is transmitted, the greater will be the effect on the component and the more marked the color. Light which has traversed a depth of two meters of distilled water has only a very slight blue color, hence it can be said that in pure water all of the component colors are transmitted with almost equal facility. The color standards at first used on the Boston Water Works were prepared by diluting portions of a highly colored water with distilled water until the colors matched those produced by nesslerizing varying amounts of an ammonia solution (oor Mg NH, per cc.) in fifty cubic centi |