How the Earth’s Rotation Is Utilized
Any wheel rotating at a high speed about its own axis, and free to place itself in any plane, is called a Gyroscope. The Gyroscope is the instrument which utilizes the earth’s rotation as a force to direct the course of ships.
Suppose you were to place such a small wheel supported by its axis upon a larger wheel which also is revolving. The rotation of the larger wheel would so influence the smaller wheel that its axis would point in the same direction as the axis of the larger wheel. Why this is the case does not concern us here. Let it suffice that the larger wheel will cause the smaller wheel to behave in this manner. This is in accordance with a natural law. This law operates as unfailingly as the law which causes an unsupported body to fall to the ground.
Suppose the larger wheel happens to be the earth, which in reality is a revolving wheel. Suppose further, the small wheel is a Sperry Gyro-Compass. In accordance with this natural law just outlined the smaller wheel, or Gyro-Compass, will point its axis in the same direction as the axis of the earth, or, in other words, to the true or geographical North Pole. This explanation of the principle of gyroscopic motion is necessarily crude. The principle itself has been established beyond any reasonable doubt. It can be proved by mathematics to the satisfaction of the most exacting scientist and has been demonstrated, throughout the navies of the world, to practical seamen.
The final result is that we have a principle which enables us to construct an instrument which will place itself in the true geographic north and south meridian, and that it responds to no influence or impulse other than the earth’s unvarying rotation.
Galley-slaves drove the Triremes of ancient Rome.
FIGURE 1.