GYROSCOPIC COMPASS METHODS OF SURVEYING 211 



too high and the gyroscope oscillates over the meridian 

 out again. As the north axis then dips below the horizon 

 a back oscillation sets in. To decrease these oscillations 

 sufficiently rapidly a damping device is provided with 

 the gyrocompass. In Anschiitz's method the suspension 

 of the compass is obtained by having it connected to a 

 body which floats in quicksilver. Then at any azimuth 

 of the gyrocompass the buoyancy of the mercury takes up 

 the gravitational force, acting through the earth's rotation 

 on the one extremity of the axis, in the form of a pull 

 upward, and that on the other end is compensated as a 

 pull downward by its proper weight. 



The Kiel Nautical Instrument Company's Gyroscopic 

 Compass for Borehole Surveys. — This apparatus^ was 

 formerly introduced for warships and 

 submarines by the firm Anschiitz of 

 Kiel. Indeed, it alone made long- 

 distance underwater navigation 

 possible. 



It is let into the hole on a cable and 

 2-m. measurements are taken with it. 

 It is held centrally by guide brushes to 

 maintain always the same vertical in 

 the hole. A measuring box (Fig. 147) 

 has two pendulums arranged to rotate 

 about the axis of the apparatus; they 

 swing in two planes at right angles to 

 one another and a small gyrocompass 

 adjusts the measuring case so that one 

 pendulum swings in the east-west and 

 the other in the north-south direction 

 regardless of how the apparatus turns 

 on being let down. Figure 148 is a 

 schematic view of the measuring box 

 with an east-west pendulum which hangs vertical while the 

 box is inclined with the hole. (The dip here is exaggerated 



1 Martienssen, 0., Eledrotechnische Ztschr., Heft 24, p. 462, 1920; p. 

 694, 1919; and pp. 862, 887, 1911. 



Fig. 147. Fig. 148. 



