i2 4 A WONDER WHICH MIGHT BE. 



To sum up; it was recognised that the angle made by 

 the axis of the terrestrial poles, with the axis of the poles 

 of the Ecliptic, far from remaining constantly equal to itself 

 (the amount was 23 27' 30" in the middle of the present 

 century), varies by 0^.48 yearly, and that this angle itself 

 experiences a variation whose mean value is 48" in a century. 

 It sometimes exceeds this mean value, and sometimes falls 

 below it, by an amount which rises to nearly 9". 65. Thus, 

 while describing, in an interval of 25,000 to 26,000 years, 

 its curve around the poles of the Ecliptic, the earth's axis 

 describes, from east to west, a small ellipsis in the space of 

 about eighteen and two-third years, and imperceptibly 

 changes, moreover, its angle of inclination. 



But, in fine, what is the true cause of all these movements ? 



Were the earth a perfect sphere, were all its radii of 

 equal length, the effect of the universal ponderation would 

 make itself felt as if all the material molecules were concen- 

 trated at a single point the centre j and, apart from this 

 ponderation, which exercises itself in the direct ratio of 

 the masses, and in the inverse ratio of the square of the 

 distances, nothing exists which would sway our globe in 

 one direction rather than in another, no precession of the 

 equinoxes would take place, the plane of the Ecliptic would 

 invariably coincide with the plane of the Equator, and an 

 eternal spring would smile on the fortunate earth. The 

 dream of the poet would be realised, and light would 

 spread 



" Through all the seasons of the golden year." 



