An imaginary, cylindrical plate of infinite radius and of thickness equal to the elevation of a particular gravity station, placed with its upper surface horizontal at the gravity station. Its density is usually taken to be 2. 67 g/cc. The attraction of the Bouguer plate at the gravity station is roughly equal to the attraction there of all matter having elevations between zero and the elevation of the gravity station. The gravitational acceleration attributable to the plate is 2πGdH, where G is the gravitational constant, d is the average density of the matter in the plate and H is the thickness of the plate. Its attraction corrects (approximately) for the error made in computing the free air anomaly when the mass between the point and the geoid is ignored.