It contains a list of the gauging stations maintained on the islands, estimates of the daily and monthly discharge of the streams, and the results of studies of rainfall at many points. Water-Supply Paper 318 gives the results of water-resource investigations in Hawaii for the years I9O9-I9ti, Water-Supply Paper 336 the work for 1912 , and 373 the work for I9I 3, These reports will be valuable to engineers and others engaged in developing the water resources of the islands. Water-Supply Papers 318 and 373 are no longer available for free distribution, but may be purchased from the Superintendent of Documents, Washington, D. C., for 5 Β° cents and 4o cents, respectively. Copies of Nos. 336 and 43 Β° may be obtained without cost on application to the Director, lJnited States Geological Survey, Washington, D. C.
Color from the Physical Point of View. H. C. RICHARDS.
(Proceedings of the Illuminc~ting Engineering Society, October ii, I917. ) The color of light may be expressed in terms of its hue, brightness, and saturation; or it may be defined by the relative amounts of three standard colors, as red, green, and blue, which must be added to produce the same impression on the eye. But these are more or less subjective definitions. From a physical point of view the character of a light (i.e., its color) is determined by the distribu-