The instrument used in carrying on the work of detecting leakage and waste of water in New York City is called a pitometer, and was especially designed by Edward S. Cole, M. Am. Soc. M. E., for water-waste detection in cities, also for measuring the flow of water in pipes from four to fortyeight inches in diameter by inserting the tubes of the pitometer into the main through an ordinary one-inch corporation. The instrument is a combination of the pilot tube and a photo-recorder, and complete, consists of the pilot orifices and a differential U tube, together with a revolving drum, covered with velox paper, a suitable lamp and a pressure gauge attachment. The instrument is extremely simple. Its photo-recorder may be handled easily without the use of a dark room by any one at all familiar with photography. The photorecord produced is eighteen inches long and ten inches wide and is a continuous photograph or record of the rate of flow of water in the main over a period of twenty-four hours. When it is desired to measure the rate of flow in the main at any point, the main is tapped with an ordinary one-inch corporation, which is all the preparation necessary for the pitometer. The instrument is then attached to this one-inch corporation, the velox paper placed on the drum, the lamp lighted and the photo-record has begun. This continues over a period of twenty-four hours, when the record is removed. Upon this record are shown at once the variaitons in the flow and the corresponding changes in static pressure within the pipe, thus interpreting the cause of any change in the flow, a feature of great importance.