180 THE GREEK ASTRONOMY. 



ing sphere to the Sun as well as to the Moon, 

 of which it is difficult to understand the meaning, 

 if Aristotle has reported rightly of the theory ; for 

 it would be absurd to ascribe to Eudoxus a know- 

 of the motions by which the sun deviates from 

 the ecliptic. Calippus conceived that two addi- 

 tional spheres must be given to the sun and to 

 the moon, in order to explain the phenomena: 

 probably he was aware of the inequalities of the 

 motions of these luminaries. He also proposed an 

 additional sphere for each planet, to account, we 

 may suppose, for the results of the eccentricity of 

 the orbits. 



The hypothesis, in this form, does not appear 

 to have been reduced to measure, and was, more- 

 over, unnecessarily complex. The resolution of the 

 oblique motion of the moon into two separate mo- 

 tions, by Eudoxus, was not the simplest way of 

 conceiving it; and Calippus imagined the con- 

 nexion of these spheres in some way which made 

 it necessary nearly to double their number ; in this 

 manner his system had no less than 55 spheres. 



Such was the progress which the Idea of the 

 hypothesis of epicycles had made in men's minds, 

 previously to the establishment of the theory by 

 Hipparchus. There had also been a preparation 

 for this step, on the other side, by the collection of 

 Facts. We know that observations of the eclipses 

 of the moon were made by the Chaldeans 367 B.C. 

 at Babylon, and were known to the Greeks; for 



