206 DEEP BOREHOLE SURVEYS AND PROBLEMS 



about which it spins unaltered in direction whether rotating 

 or not. If spinning it resists any attempt to alter the direc- 

 tion of its axis, and the gyroscopic torque dominates when 

 the gyroscope is given a very high speed as is common in 

 borehole practice. This precession is so important in 

 borehole gyrocompasses that it appears to merit fuller 

 detail. 



At the beginning of this century several trials were made 

 to establish a gyrocompass. Doctor Anschiitz-Kaempfe 

 succeeded in bringing out a gyroscopic compass which 

 maintained its direction for a long time — 24 hr. — in the 

 laboratory. He however recognized that it was extra- 

 ordinarily difficult, perhaps impossible, to create a gyro- 

 scope complete and perfect in equilibrium; he therefore, 

 in 1906, added to the gyroscope with three degrees of 

 freedom one with two degrees of freedom and in this way 

 arrived, by progressive simplification, at his first gyroscopic 

 compass with only one high-speed wheel and with damped 

 oscillations. In the most recent form of the Anschiitz 

 compass for nautical purposes there are three similar wheels 

 which compensate the regular oscillations of the ship. 



Precession. — When a simple wheel disc rotates and no 

 lateral force or torque is exerted upon it, it persists in its 

 position because every particle of mass in the disc endeavors 

 to remain in the plane set up. This inertia grows with the 

 mass of the disc and with the angular velocity of the rota- 

 tion. If a torque is exerted on the quiescent disc (which 

 can be imagined as an upward pull on one axis end or a 

 downward pressure on the other end) the plane will incline 

 laterally. 



If a torque or lateral pressure be now appUed to the disc 

 when rotating, we have the inertia of the disc on the one 

 hand and the inclination of the tilt on the other, so that it is 

 a question of what will be the result in the motion due to 

 these two factors acting simultaneously. Let us consider 

 Haussmann's^ simple presentation of these important 

 facts, which we have slightly modified for our purpose. 



1 Ibid., p. 51. 



