air-box, Fig. 172. The air-box is shown in detail in Fig. 173. The pipes are joined to the north working and to the north damping bottles, and to the south working and south damping bottles as indicated.
130. Absence of Latitude Error. - In northern latitudes, the north-seeking end of the gyro-axle will have a resting position above the horizontal plane through the center of the gyro-wheel. In southern latitudes, it will have a resting position below the horizontal. The natural tilt of the spin-axle is the amount required 'to cause precession at the rate at which the meridian is turning, that is the amount required to cause the axle to precess into the resting position after it has been displaced from that position. If the torque due to the pendulousness of the gyro-compass be small, the spin-axle will have the same resting position that it would have if the pendulousness were greater, but the speed with which the spin-axle precesses will be slower.
The method employed to damp the vibrations of the Brown gyrocompass is equivalent to a diminution of the degree of pendulousness of the gyro-system while it is oscillating through the meridian plane. It does not oppose the tilt of the gyro-axle required to precess the gyro-axle to the normal resting position. It follows that the Brown gyro-compass is without latitude error (Art. 110).
131. The Meridian-Steaming Error. - Every gyro-compass is subject to an error depending upon the meridian component of the velocity of the ship (Art. 111). No means are provided for correcting the indication of the Brown master gyro-compass, but the meridian-steaming error is allowed for in the repeater compasses