

Mr. Sidney G. Brown 



Jan. 30, 



and will continue to move until the effect of the earth arrests and 

 reverses the motion. 



The compass will therefore continue to swing through the north 

 position with constant amplitude backwards and forwards, undamped. 



To render the compass of use some method of damping the swing 

 must be introduced, so that the compass may finally settle on the 

 north. 



This damping can be carried out by means of friction — prefer- 

 ably fluid friction — between the vertical spindle and its support, but 

 although this will damp the swings it is inadmissible, because the 

 movements of the ship would react through the friction and cause 

 errors in the reading:. 



Fig. 4. — Anschutz early Form of Gyro-Compass. 



Anschutz, in his early form of compass, by use of an air blast 

 rid of this connection with the ship. The air blast was arranged 

 to oppose the movement in " azimuth " when the wheel tilted, and 

 thus he obtained an effective method of damping. The strength of 

 the air blast, which varies proportionally to the tilt, should be 

 nothing when the compass is at rest on the north — that is, when the 

 tilt is nothing— and this would be true with the compass on the 

 equator. 



In other latitudes, however, the compass rests at the north with 

 a tilt still remaining. It does not come back to the horizontal 

 position because the axis of the wheel is trying to set itself parallel 

 te that of the earth. This leaves a residual air blast continuous! v 



