Discussion on “sterilization of water by ultra-violet rays of the mercury-vapor quartz lamp” (Von Recklinghausen), Detroit, Mich., June 26, 1914. (see proceedings for June, 1914)

Morgan Brooks: I notice one point, that is not of very great importance, that perhaps might lead to error. The author speaks of the light varying inversely as the square of the distance. That is true in the case of point source, but not true of line source. If the light is of any appreciable length in proportion to the tank, or the vehicle which is used in conveying the water, it will vary more nearly in inverse proportion to the distance, which will make a difference in some cases.