Solar System. 55' 



F it, which at any time is turned towards 

 the sun, can be enlightened by him at 

 that time : it is some part of this enlight- 

 ened half of the earth that the moon's 

 shadow falls on in a solar eclipse. 



In any year the number of eclipses of 

 both luminaries cannot be less than two,, 

 nor more than six* Eclipses of the sun 

 are more frequent than of the moon, be- 

 cause the sun's ecliptic limits are greater 

 than the moon's ; yet we have more visi- 

 ble eclipses of the moon than of the sun, 

 because eclipses of the moon are seen 

 from all parts of that hemisphere of the 

 earth which isnext them, and are equally 

 great to each of those parts ; but the sun's 

 eclipses are visible only to that small 

 portion of the hemisphere where the 

 moon's shadow falls. 



An eclipse of the moon can never hap- 

 pen but at the time of full moon. 



An eclipse of the sun always begins on 

 the western, and ends on the eastern side ; 

 because the moon, moving in her orbit 

 from west to east, necessarily first ar- 

 rives and touches the sun's western limb, 

 and goes off at the eastern ; that of the 



