System of the Universe. 255 



philosophers followed his opinion ; among others 

 was Claudius Ptolemy, the celebrated astronomer 

 and mathematician of Pelusium in Egypt, already 

 mentioned, who lived in the beginning of the 

 second century of the Christian sera. It is, how- 

 ever, incredible that, the true system of the world 

 having been once discovered, the hypothesis by 

 which the earth is supposed to be the centre of 

 the celestial movements should have again pre- 

 vailed ; for though this hypothesis accords with 

 some of the most obvious appearances, and seems 

 to agree at first with the simplicity of nature, yet 

 it is impossible on that system to account for all 

 the celestial phsenomena. 



Ptolemy, who has given the name to this system, 

 endeavours to prove that the earth T ( PL XXIII. 

 fig. 105) is immoveable as the centre of the 

 universe ; and he places the other planets round 

 about her in the following order, beginning with 

 those which he believes the next to the Earth : 

 the Moon D , Mercury $ , Venus ? , the Sun 0, 

 Mars $ , Jupiter 1, and Saturn T? 5 till he comes 

 at length to the fixed stars. When, however, 

 astronomers had begun to observe the planets, 

 they remarked that Mercury and Venus are 

 sometimes nearer and sometimes farther from 

 us than the Sun ; and that Venus never departs 

 from the Sun more than about forty-seven de- 

 grees and a half; and Mercury about twenty- 

 eight degrees and a half, and sometimes much 

 less. But it is evident that if these two planets 



