SYSTEM OF COPERNICUS. 119 



generally known as the Copernican system. But four-and- 

 twenty centuries prior to the epoch of Nicholas Copernicus, 

 it was taught by the "Samian sage," Pythagoras, and his 

 disciples. The system then in acceptance, however, imposed 

 upon them the necessity of silence. Ptolemseus was acquainted 

 with it, but endeavoured to turn it into ridicule. " There are 

 people," he says, "who pretend that heaven is immovable, 

 and that it is earth which revolves on its own axis ; evidently 

 these individuals are unaware how supremely absurd is their 

 opinion (navfj* ysXo/o'raroi/)." And it was in the name of 

 logic and mathematics that Ptolemaeus thus treated the 

 Pythagoreans ! 



In the system of Copernicus, the diurnal movement of 

 the right sphere, it is the earth's rotation upon its own 

 axis which, being prolonged into the heavens, marks there, 

 by its extremities, what are called the Poles of the world, 

 just as the Equator of the world is simply the prolongation 

 of the terrestrial Equator. As for the Equator of the 

 oblique sphere (the Ecliptic), in which the sun apparently 

 moves, it is, in reality, the identical plane in which the 

 earth moves during its annual revolution round the sun. 

 Now, in this movement of translation, the axis of the 

 earth does not remain constantly parallel to itself; it 

 deviates, very slightly, it is true, and so as to be scarcely 

 perceptible to several generations of men. It is then quite 

 natural that our successors should see, for a long time to 

 come, the northern pole of the starry sphere near the ex- 

 tremity of the tail of Ursa Minor. But, two thousand years 



