A RETROSPECTIVE GLANCE 



suffice to summarize a story the details of which have 

 made up our recent chapters. 



In the field of cosmology, Greek genius has demon- 

 strated that the earth is spheroidal, that the moon is 

 earthlike in structure and much smaller than our 

 globe, and that the sun is vastly larger and many 

 times more distant than the moon. The actual size of 

 the earth and the angle of its axis with the ecliptic 

 have been measured with approximate accuracy. It 

 has been shown that the sun and moon present in- 

 equalities of motion which may be theoretically ex- 

 plained by supposing that the earth is not situated 

 precisely at the centre of their orbits. A system of 

 eccentrics and epicycles has been elaborated which 

 serves to explain the apparent motions of the heavenly 

 bodies in a manner that may be called scientific even 

 though it is based, as we now know, upon a false 

 hypothesis. The true hypothesis, which places the 

 sun at the centre of the planetary system and postu- 

 lates the orbital and axial motions of our earth in 

 explanation of the motions of the heavenly bodies, has 

 been put forward and ardently championed, but, un- 

 fortunately, is not accepted by the dominant thinkers 

 at the close of our epoch. In this regard, therefore, a 

 vast revolutionary work remains for the thinkers of a 

 later period. Moreover, such observations as the 

 precession of the equinoxes and the moon's evection 

 are as yet unexplained, and measurements of the 

 earth's size, and of the sun's size and distance, are so 

 crude and imperfect as to be in one case only an ap- 

 proximation, and in the other an absurdly inadequate 

 suggestion. But with all these defects, the total 



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