694 COSMOS. 



fixed in a central point, while the sun revojves around it as a 

 circling planet, attended by two satellites, Mercury and 

 Venus. Such a view of the structure of the world might, 

 indeed, prepare the way for that of the central force of the 

 sun. There is, however, nothing in the Almagest, or in the 

 works of the ancients generally, or in the work of Copernicus 

 De Revolutionibus, which justifies the assertion so confidently 

 maintained by Gassendi, of the perfect resemblance existing 

 between the system of Tycho Brahe and that which has been 

 ascribed to Apollonius of Perga. After Bockh's complete 

 investigation, nothing further need be said of the confusion 

 of the Copernican System with that of the Pythagorean, Phi- 

 lolaus, according to which, the non-rotating earth (the 

 Antichthon or opposite earth, being not in itself a planet, but 

 merely the opposite hemisphere of our planet) moves like the 

 sun itself round the focus of the world, the central fire, or 

 vital flame of the whole planetary system. 



The scientific revolution originated by Nicolaus Coper- 

 nicus has had the rare fortune (setting aside the temporary 

 retrograde movement imparted by the hypothesis of Tycho 

 Brahe) of advancing without interruption to its object, 

 the discovery of the true structure of the universe. The rich 

 abundance of accurate observations furnished by Tycho 

 Brahe himself, the zealous opponent of the Copernican sys- 

 tem, laid the foundation for the discovery of those eternal 

 laws of the planetary movements which prepared imperish- 

 able renown for the name of Kepler, and which, interpreted 



Almagest should be the only source from whence the complete Tychonic 

 view is ascribed to Apollonius, we may consider that Gassendi haa 

 gone too far in his suppositions, and that the case is precisely the same 

 as that of the phases of Mercury and Venus, of which Copernicus 

 spoke (lib. i. cap. 10, p. 7,b, and 8, a,) without decidedly applying them 

 to his system. Apollonius may, perhaps, in a similar manner have 

 treated mathematically the assumption of tho retrogressions of the 

 planets under the idea of a revolution round tne sun, without adding 

 anything definite and general as to the truth of this assumption. The 

 difference of the Apollonian system, described hy Gassendi, from that of 

 Tycho, would only be, that the latter likewise explained the inequalities 

 of the movements. The remark of Robert Small, that the idea which 

 forms the basis of Tycho's system was by no means unfamiliar to the 

 mind of Copernicus, but had rather served him as a point of transition 

 to his own system, appears to me well founded." 



