

System of the Universe. 255 



round her own axis, which rendered useless that 

 prodigious celerity in the motions of the heavenly 

 bodies, of which I have just spoken, and by these 

 means simplified the system. This motion once 

 admitted, it was no violent step to admit of 

 a second motion of the Earth in the ecliptic. 

 These two motions explain, with the utmost faci- 

 lity, the phenomena of the stations and motions 

 of the planets. According to Copernicus, then, 

 the Sun S (PI. XXIV.%. 107) is the centre of our 

 planetary system, and the planets turn about him 

 in the order following ; Mercury g , Venus ? , 

 the Earth J, Mars , Jupiter 1, Saturn T? , 

 (to which we may add Ceres, Pallas, Juno, Vesta, 

 and the Georgium Sidus $) at a distance from 

 the Sun, nearly as the numbers 4, 7, 10, 15, 52, 

 95, 191* The Moon, also, he supposed to be 

 carried round the Earth in an orbit which goes 

 along with the Earth in her annual revolution 

 round the Sun. In like manner about Jupiter, 

 Saturn, and the Georgium Sidus, are the -four 

 satellites of the first, the five satellites of the 

 second, and the two satellites of the third ; none 

 of which, however, were known to Copernicus. 



Although the celestial phenomena explain 

 themselves with the greatest facility according to 

 the system of Copernicus, and though observa- 

 tion and reason are equally favourable to it, yet 

 it was rejected by an able astronomer who flou- 

 rished soon after his own time. Tycho-Brahe, 

 from the experiment that a stone thrown from a 



