ASTRONOMY. 157 



b. The Evening and Morning Star, or the Hesperus 

 and Phosphorus of the Greeks, were at first sup- 

 posed to be different. The discovery that they are 

 the same is ascribed to PYTHAGORAS. 



155. This planet, when an evening star, and 

 at her greatest distance from the sun, or at 

 what is called her Greatest Elongation, appears, 

 through the telescope, to have a semicircular 

 disk, like the moon in the last quarter, with its 

 convexity turned to the west. From that time, 

 during her approach to the sun, her splendour 

 increases for a while, though the quantity of 

 the illuminated disk diminishes, like the moon 

 in the wane ; and at the same time, her dia- 

 meter, measured by the distance of the horns, 

 increases. 



a. At the time of her greatest elongation, Venus is 

 stationary with respect to the sun, or has the same 

 motion in longitude. After that, her motion in 

 longitude becomes slower than the sun's, and she 

 comes nearer to the sun, as just remarked. At a 

 certain point she becomes stationary with respect 

 to the fixed stars, having no motion in longitude. 

 After that, her motion becomes retrogade in re- 

 spect of the fixed stars, and is directed west- 

 ward. 



b. Venus at last approaches the sun, so as to be lost 

 in his light ; and after some time, appears on the 



west 



