i6 



A Short History of Astronomy 



[CH. I. 



nearer to the earth than others must have been suggested 

 by eclipses ( 17) and occultations, i.e. passages of the 

 moon over a planet or fixed star. In this way the moon 

 would be recognised as nearer than any of the other 

 celestial bodies. No direct means being available for 

 determining the distances, rapidity of motion was employed 

 as a test of probable nearness! Now Saturn returnsTo' the 

 same place among the stars in about 29^ years, Jupiter in 

 12 years, Mars in 2 years, the sun in one year, Venus in 225 



2 SOS. 



2 303 



FIG. 6. The apparent path of Jupiter from Oct. 28, 1897, to 

 Sept. 3, 1898. The dates printed in the diagram shew the 

 positions of Jupiter. 



days, Mercury in 88 days, and the moon in 27 days; and 

 this order was usually taken to be the order of distance, 

 Saturn being the most distant, the moon the nearest. The 

 stars being seen above us it was natural to think of the 

 most distant celestial bodies as being the highest, and 

 accordingly Saturn, Jupiter, and Mars being beyond the 

 sun were called superior planets, as distinguished from the 

 two inferior planets Venus and Mercury. This division 

 corresponds also to a difference in the observed motions, 

 as Venus and Mercury seem to accompany the sun in its 



