186 THE GREEK ASTRONOMY. 



and perpetually recurring test; and thus proved the 

 soundness of the theory on which the tables were 

 calculated. 



The Moon's Eccentric. The moon's motions 

 have many irregularities ; but when the hypothesis 

 of an Eccentric or an Epicycle had sufficed in the 

 case of the sun, it was natural to try to explain, in 

 the same way, the motions of the moon ; and it was 

 shown by Hipparchus that such hypotheses would 

 account for the more obvious anomalies. It is not 

 very easy to describe the several ways in which 

 these hypotheses were applied, for it is, in truth, 

 very difficult to explain in words even the mere 

 facts of the moon's motion. If she were to leave a 

 visible bright line behind her in the heavens wher- 

 ever she moved, the path thus exhibited would be 

 of an entremely complex nature ; the circle of each 

 revolution slipping away from the preceding, and 

 the traces of successive revolutions forming a sort 

 of band of net-work running round the middle of 

 the sky 2 . In each revolution, the motion in longi- 

 tude is affected by an anomaly of the same nature 

 as the sun's anomaly already spoken of; but besides 

 this, the path of the moon deviates from the ecliptic 

 to the north and to the south of the ecliptic, and 

 thus she has a motion in latitude. This motion in 

 latitude would be sufficiently known if we knew the 



2 The reader will find an attempt to make the nature of this 

 path generally intelligible in the Companion to the British 

 Almanack for 1834. 



