420 ASTRONOMY. 



they will divide the ecliptic into equal parts. Upon 

 the ecliptic is reckoned the longitude of any fixed 

 star, beginning to reckon at that point where the 

 ecliptic and the equator intersect each other in the 

 vernal equinox, called the first point of Aries ; 

 and the arch of any of the circles of celestial lon- 

 gitude intercepted between any star and the eclip- 

 tic, is the latitude of that star. The equator is 

 divided into degrees, but they are called degrees 

 of right ascension ; and from it to the poles the 

 degrees of declination are reckoned upon the meri- 

 dian of the place. 



We have now described* the principal lines and 

 points on the celestial sphere, as generated by the 

 apparent motions of the heavenly bodies, in which 

 we have supposed what appears at first sight to be 

 the case, viz. the earth stands still while all the 

 heavenly bodies revolve round it. This will make 

 no difference with regard to these circles in the 

 heavens ; for it will be the same thing with respect 

 to them, whether the earth be at rest, and the hea- 

 venly bodies move round it, or whether the latter 

 remain still, and the earth, as we shall afterwards 

 see, move round its axis once every twenty-four 

 hours. 



The earth, upon which we live, was long consi- 

 dered as an extensive plane, and mankind had an 

 obscure notion of its being supported on some sort 

 of scaffolding or pillars, though they could not tell 

 what supported these. The heavens above it, in 

 which the sun, moon, and stars, appeared to move 

 daily from east to west, were conceived to be at no 

 great distance from it, and to be only designed for 

 the use and ornament of our earth. The natives 

 of India and the Eastern countries appear to have 



