Consists essentially of an aneroid barometer and a revolving drum. The movement of the evacuated spring can is transmitted and magnified through a system of levers so that it is finally traced by means of a stylo on the graph paper attached to the revolving drum. The drum is rotated by clockwork, and can be of either the 24-h or the 7-day type. The graph paper is usually marked off in hourly intervals, so that a complete record of the atmospheric pressure at any instant may be obtained. These barographs are used extensively in mining and in meteorological offices.