ASTRONOMY. 417 



so that the one being known, and subtracted from 

 90°, it will give the other ; therefore, the elevation 

 of the pole at any place is the complement of the ele- 

 vation of the equator, or what that elevation wants 

 of 90°. It follows from hence, that the elevation 

 of the equator is equal to the distance from the 

 pole to the zenith ; for the elevation of the equator 

 is the difference between that of the pole and 90° 

 (the same elevation subtracted from 90°, gives its 

 distance from the zenith). A little attention will 

 soon convince you, that the sun does not rise 

 always at the same point of the heavens. Thus, if 

 you commence your observations on the sun, for 

 instance in the beginning of March, you will find 

 him appear to rise more to the northward every 

 day, to continue longer above the horizon, and to 

 be more vertical or higher at mid-day. This con- 

 tinues till towards the end of June, when he moves 

 backward in the same manner, and continues this 

 retrograde motion till near the end of December, 

 when he begins to move forward, and so on. It is 

 from this change in the sun's place, and from his 

 height being so much greater in summer than in 

 winter, that the different length of the days and 

 nights, and the vicissitudes of seasons are owing. 

 We cannot observe the sun's motion among the 

 fixed stars, because he darkens the heavens by his 

 splendor, and effaces the feeble light of those stars 

 that are in his neighbourhood ; but we can observe 

 the instant of his coining to the meridian, and his 

 meridianal altitude ; we can also compute what 

 point of the starry heavens comes to the same me- 

 ridian at the same time, and with the same alti- 

 tude. The sun must be at that point of the starry 

 heavens thus discovered. Or, we can observe that 

 point in the heavens which comes to the meridian 

 vol. r. E E 



