THE ANSCHUTZ GYRO-COMPASS 225
electrode A, A'. This equatorial electrode is divided by two vertical gaps. One of these halves is further divided into two by a horizontal gap. All three parts are electrically connected. The spherical shell is provided with two polar electrodes Pt, P2, and two ring-shaped electrodes K, K'. The electrodes consist of thin layers of hard rubber charged with carbon and vulcanized on the metal globes. All electrodes are inlaid in the insulating hard rubber coatings of the outside of the gyro-globe, or the inside of the spherical shell, so as to be flush with the spherical surfaces.
The volume of the gyro-globe is such that the weight of the liquid displaced by it is nearly equal to the weight of the globe. Any tendency of the gyro-globe to sink or to move laterally from the central position within the surrounding sphere is prevented by the magnetic force of repulsion developed by the interaction of the magnetic field about an alternate current carrying coil C, Figs. 176 and 177, within the globe, and the magnetic field of eddy currents induced in a conducting saucer-shaped electrode P2 forming part of the lower side of the outer spherical shell. The centralizing coil produces a conical repelling field directed toward the center of the gyro-globe.
The centralizing coil C and the three-phase motor of the two gyros G1, G2, Fig. 177, are joined to the equatorial electrode A and to the two polar electrodes, as indicated in Fig. 176. A threephase current passes from the electrodes P,, P2 and K, K' on the inside of the outer spherical shell, through the thin layer of electrolyte, to the corresponding electrodes P1, P2, and A, A' on the outside of the gyro-globe, Fig. 175.
Lubrication of the moving parts within the gyro-globe is effected by wicks dipping into a pool of oil in the bottom of the globe, x, x', Fig. 177a.
The gyro-globe is exhausted of air and then filled with dry hydrogen at atmospheric pressure. The use of hydrogen instead of air results in several advantages: (a) the oil required for the operation of the apparatus within the globe suffers no chemical change even during months of continuous service; (b) since windage loss is proportional to the density of the surrounding gas, the windage loss with hydrogen is about one-fourteenth that which would occur if the globe were filled with air at the same pressure; (c) since the thermal conductivity of hydrogen is about seven times that of air and the diffusivity is about four times that of air, it follows that