INDUCTIVE EPOCH OF HIPPARCHUS. 185 



case ; and the genius of the discoverer appeared, as 

 such genius usually does appear, in his perceiving 

 how small a number of facts, rightly considered, 

 were sufficient to form a foundation for the theory. 

 The number of days contained in two seasons of 

 the year sufficed for this purpose to Hipparchus. 

 " Having ascertained," says Ptolemy, " that the time 

 from the vernal equinox to the summer tropic is 

 94?L days, and the time from the summer tropic to 

 the autumnal equinox 92J days, from these pheno- 

 mena alone he demonstrates that the straight line 

 joining the centre of the sun's eccentric path with 

 the centre of the zodiac (the spectator's eye) is 

 nearly the 24th part of the radius of the eccentric 

 path; and that its apogee precedes the summer 

 solstice by 24J degrees nearly, the zodiac con- 

 taining 360." 



The exactness of the Solar Tables, or Canon, 

 which was founded on these data, was manifested, 

 not only by the coincidence of the sun's calculated 

 place with such observations as the Greek astrono- 

 mers of this period were able to make, (which were 

 indeed very rude,) but by its enabling them to cal- 

 culate solar and lunar eclipses; phenomena which 

 are a very precise and severe trial of the accuracy 

 of such tables, inasmuch as a very minute change 

 in the apparent place of the sun or moon would 

 completely alter the obvious features of the eclipse. 

 Though the tables of this period were by no means 

 perfect, they bore with tolerable credit this trying 



