ANALOGOUS TO THOSE OF THE EARTH. 237 



In comparing these two electro-magnets, we find 

 that the gyroscope, like the earth, has its diamag- 

 netic current and polarity; its axial and orbital 

 revolutions ; its compensating movement and rela- 

 tive static and dynamic conditions ; the symmetri- 

 cal or equilibrial placing of its axis, answering to 

 the earth's equinoctial position when the orbital 

 revolution, of the gyroscope at least, ceases; a 

 declination of the axis when the orbital revolution 

 of the gyroscope is in the same direction as the 

 underside of the disc ; and an upward inclination 

 of the axis when the orbital revolution is re- 

 versed and is in the direction of the upper side 

 of the disc, answering to the perihelion and aphe- 

 lion positions. 



The rotation of both the earth and the gyro- 

 scope is in a constant direction in the three different 

 positions of their axes during their orbital revolu- 

 tions ; and as the gyroscope in opposite positions 

 of its*axis moves in opposite directions, may we 

 not infer as a possibility similar movements for 

 the earth ? ' 



" Terrestrial analogies afford us a very sure guide 

 in the midst of many perplexities," and the com- 

 bined movements of the gyroscope fulfil each 

 function as completely as the like movements of 



1 " To say that the equinox falls back, or retrogrades is the same as 

 saying that the plane of the equator has varied in position ; and as the 

 axis of the earth is always perpendicular to this plane, it follows that 

 this axis has not remained rigorously parallel to itself." The Heavens, 

 p. 456. Guillemin. 



