78 FROM NEBULA TO NEBULA 



To check the matter, and to fix these relations the 

 more firmly in the memory, change your position 

 mentally to the geographical north pole of our earth and 

 look down northwardly toward the Vertex ; and, since the 

 latter is only a blank, fancy a great star there placed, and 

 then in your mind's eye watch its tracings on the dome of 

 the northern sky. What do you see now? You see this 

 fictitious star, projected, describe around the so-called 

 north pole of the ecliptic, in a contra-clockwise direction, 

 a circle 23j^ in radius; exactly corresponding with the 

 inclination of the earth's axis, and consuming for its 

 execution the aforesaid period of 26,000 years. 



In fine, the true dynamical pole of the ecliptic is the 

 Vertex, but this, being more proximate to us than the 

 celestial sphere, its projection upon the northern sky pro- 

 duces, by virtue of our movement in a great circle, the 

 phenomenon of precession which we are now discussing. 



In order that the Vertex might coincide in alignment 

 with the celestial pole of the ecliptic, it would have to be 

 viewed from a point in the axis of the Gravisphere, a posi- 

 tion which no member of our system, of course, can ever 

 occupy. 



It must not be supposed that I mean to imply that the 

 stars that successively mark the terrestrial pole as 

 Polaris does now (approximately), are posed on the Arc- 

 tic Circle of the Gravisphere. Far from it. That Circle 

 is merely the boundary of a particular cross section of the 

 inverted cone whose apex is the Vertex and whose real 

 base rests on the celestial sphere, which is to say, at in- 

 finity. A star at any distance, in the line of the cone's 

 side, would appear as if on this Circle. 



Let it now be recalled that the sun's orbit along the 

 great Antarctic Circle is not a closed curve, seeing that 

 he is constantly falling Vertex-ward. It is possible to 

 determine how fast he is falling and to state that in 26,000 

 years, or one circuit, he will fall about double the distance 

 of the Vertex, describing incidentally, of course, a great 

 spiral coil. This, however, need alarm no one, for the 

 simple reason that the Vertex is a kind of will-o '-the- 

 wisp. You cannot imagine a point in space where a body, 



