ITS EARLIEST STAGES. 169 



and full in position (that is a quadrant from the 

 sun) she would be somewhat more than a half 

 moon ; and the place when she was dichotomized, 

 that is, was an exact semicircle, the bright part 

 being bounded by a straight line, would depend 

 upon the sun's distance from the earth. Aristar- 

 chus endeavoured to fix the exact place of this 

 Dichotomy ; but the irregularity of the edge which 

 bounds the bright part of the moon, and the dif- 

 ficulty of measuring with accuracy, by means then 

 in use, either the precise time, when the boundary 

 was most nearly a straight line or the exact dis- 

 tance of the moon from the sun at that time, 

 rendered his conclusion false and valueless. He 

 collected that the sun is at 18 times the distance 

 of the moon from us ; we now know that he is 

 at 400 times the moon's distance. 



It would be easy to dwell longer on subjects of 

 this kind ; but we have already perhaps entered 

 too much in detail. We have been tempted to 

 do this by the interest which the mathematical 

 spirit of the Greeks gave to the earliest astrono- 

 mical discoveries, when these were the subjects of 

 their reasonings : but we must now proceed to con- 

 template them engaged in a worthier employment, 

 namely, in adding to these discoveries. 



