profilograph

Century Dictionary and Cyclopedia

1. n. An instrument used for making an automatic record of the profile of the ground over which it moves. It consists of a light four-wheeled vehicle so arranged that as it advances a band of paper is moved mechanically over a table on top of the machine a distance corresponding to the distance traveled according to a prearranged scale of distances. Beneath the machine is suspended a pendulum always hanging vertically, and serving to actuate a pencil the point of which rests on the paper and leaves a trace upon it. Any inequality of the surface causes the machine to incline from the level, and produces a corresponding deviation from a straight line in the mark traced by the pencil. The data obtained from these indications are sufficient for reproduction to scale of the profile traversed.