The Earth considered as a Planet. 87 



When the sun arrives at the same equi- 

 noctial or solstitial point, he finishes what 

 we call the tropical year ; which, by ob- 

 servation, is found to contain 365 days 

 5 hours 48 minutes 57 seconds: and 

 when he arrives at the same fixed star 

 again, as seen from the earth, he completes 

 the sidereal year, which contains 365 

 days 6 hours 9 minutes 14~ seconds. 

 The sidereal year is therefore 2O min- 

 utes 17- seconds longer than the solar 

 or tropical year, and 9 minutes 14 1 

 seconds longer than the Julian or civil 

 year, which we state at 365 days 6 hours : 

 so that the civil year is almost a meanbe- 

 twixt the sidereal and tropical. 



The anticipation of the equinoxes, and 

 consequently of the seasons, is by no 

 means owing to the precession of the 

 equinoctial and solstitial points in the 

 heavens (which can only affect the appa- 

 rent motions, places and declinations of 

 the fixed stars) but to the difference be- 

 tween the civil and solar year, which is 

 1 1 minutes 3 seconds ; the civil year con- 

 taining 365 days 6 hours, and the solar 

 year 365 days 5 hours 48 minutes 57 

 seconds, 



