318 Astronomy. ' [Lecture 20, 



ference, especially in the time of harvest, with 

 which fanners were better acquainted than as- 

 tronomers till of late; and they gratefully ac- 

 knowledged the goodness of God, in giving 

 them an immediate supply of moonlight alter 

 the setting of the sun, for their greater con- 

 veniency in reaping the fruits of the earth, with- 

 out understanding the means by which this was 

 effected. About the equator, where there is no 

 variety of seasons, and the weather changes 

 seldom, and at stated times, moonlight is not 

 necessary for gathering in the produce of the 

 "earth. At the polar circles, where the mild 

 season is of very short duration, the autumnal 

 full moon rises at sunset from the first to the 

 third quarter. And at the poles, where the sun 

 is for half a year absent, the winter full moons 

 shine constantly without setting from the first to 

 the third quarter. 



It is easy to state in general terms that these 

 phasncmena are owing to the different angles 

 made by the horizon and different parts of the 

 moon's orbit; and that the moon can be full 

 but once or twice in a year in those parts of her 

 orbit which rise with the least angles. But to 

 explain this subject intelligibly, I must dwell 

 somewhat longer upon it. The plane of the 

 equinoctial is perpendicular to the earth's axis ; 

 and therefore, as the earth turns round its axis, 

 all parts of the equinoctial make equal angles 

 with the horizon both at rising and setting ; so 



