ITS EAKLIEST STAGES. 129 



the wants, even of the least civilized nations. But the distribution of 

 the places and motions of the heavenly bodies by means of a celestial 

 sphere with imaginary lines drawn upon it, is a step in speculative 

 astronomy, and was occasioned and rendered important by the scien- 

 tific propensities of man. 



It is not easy to say with whom this notion originated. Some parts 

 of it are obvious. The appearance of the sky naturally suggests the 

 idea of a concave Sphere, with the stars fixed on its surface. Their 

 motions during any one night, it would be readily seen, might be repre- 

 sented by supposing this Sphere to turn round a Pole or Axis ; for 

 there is a conspicuous star in the heavens which apparently stands still 

 (the Pole-star) ; all the others travel round this in circles, and keep 

 the same positions with respect to each other. This stationary star is 

 every night the same, and in the same place ; the other stars also have 

 the same relative position ; but their general position at the same time 

 of night varies gradually from night to night, so as to go through its 

 cycle of appearances once a year. All this would obviously agree 

 with the supposition that the sky is a concave sphere or dome, that 

 the stars have fixed places on this sphere, and that it revolves perpet- 

 ually and uniformly about the Pole or fixed point. 



But this supposition does not at all explain the way in which the 

 appearances of different nights succeed each other. This, however, 

 may be explained, it appears, by supposing the sun also to move amony 

 the stars on the surface of the concave sphere. The sun by his bright- 

 ness makes the stars invisible which are on his side of the heavens : 

 this we can easily believe ; for the moon, when bright, also puts out all 

 but ihe largest stars ; and we see the stars appearing in the evening, 

 each in its place, according to their degree of splendor, as fast as the 

 declining light of day allows them to become visible. And as the 

 sun brings day, and his absence night, if he move through the circuit 

 of the stars in a year, we shall have, in the course of that time, every 

 part of the starry sphere in succession presented to us as our noc- 

 turnal sky. 



This notion, that the sun moves round among the stars in a year, is 

 the basis of astronomy, and a considerable part of the science is only 

 the development and particularization of this general conception. It 

 is not easy to ascertain either the exact method by which the path of 

 the sun among the stars was determined, or the author and date of the 

 discovery. That there is some difficulty in tracing the course of the 

 sun among the stars will be clearly seen, when it is considered that no 

 Vol. 1.^9 



