218 THEORY OF THE EARTH. 



at the long run it has been remarked, that the 

 appearance of the heavens was no longer exactly 

 the same that it anciently was at the times of the 

 equinoxes and solstices. But we have never heen 

 able to observe exactly the heliacal rising of a 

 star, being always necessarily some days wide of 

 it; and people frequently speak of it, without 

 possessing a fixed datum on which to count. 

 Before Hipparchus, we find nothing, either in 

 books or in traditions, that can be submitted to 

 calculation ; and it is this which has given rise to 

 so many systems. Controversies have arisen with- 

 out a sufficient knowledge of the subject. Those 

 who are not astronomers may form ideas as beau- 

 tiful as they please of the knowledge of the Chal- 

 deans, Egyptians, &c. ; no real inconvenience will 

 result. The enterprise and knowledge of the mo- 

 derns may be lent to these nations, but nothing 

 can be borrowed from them ; for they have either 

 had nothing, or they have left nothing. Astro- 

 nomers will never derive from the ancients any 

 thing that can be of the slightest utility. Let us 

 leave to the learned their vain conjectures, and 

 confess our utter ignorance respecting things of 

 little use in themselves, and of which no monu- 

 ment remains. 



" The limits of the constellations vary according 

 to the authors which we consult. We find these 

 limits extend or contract, as we pass from Hip- 



