ON THE SOLAR SYSTEM. --^y 



that of the planet, F^is figu"- appears also, according to Dr. Hcrschel's 

 observations, to be extremely singular; deviating very considerably from that 

 of an elliptical spheroid, which is the form assumed by all the other planets 

 that appear flattened, and approaching in some degree to a cylinder with its 

 angles rounded off. Such a form can only be derived from some very great 

 irregularities in the density of the internal parts of his substance. 



The Georgian planet, discovered by Dr. Herschel in 1780, sometimes also' 

 called Herschel, and sometimes Uranus, revolves in 83:1 years, at a distance 

 from the sun equal to 19 times that of the earth. Its diameter is a little 

 more than 4 times that of the earth, and the weight of bodies at its surface a 

 little less than here. Notwithstanding its dimensions are by«no means compara- 

 tively small, it appears to us as a star of the sixth or seventh magnitude, 

 and is seldom seen by the naked eye. Its orbit approaches very near to the 

 ecliptic; its disc is said to be somewhat flattened, and it is supposed to re- 

 volve with considerable rapidity. 



These ten planetary bodies are the only ones hitherto discovered which 

 have any title to be considered as primary planets, that is, as bodies revolving 

 round the sun, in orbits so nearly circular, as to remain always within the 

 reach of bur observation. It has been conjectured that the number of 

 planets may in reality be much greater, that not only many small and perhaps 

 invisible bodies may be revolving in the intervals of the planets with 

 which we are acquainted, but that larger bodies also may belong to our 

 system, which never approach within such a distance as to be seen by us. 

 Some have even bestowed names, borrowed from the ancient mythology, on 

 these imaginary planets; but the idea of such an appropriation of terms Is 

 rather to be regarded as belonging to the regions of poetical fiction than to 

 those of solid philosophy. 



The largest and the most remote of the primary planets have their attend- 

 ant satellites, or secondary planets, accompanying them in their respective 

 revolutions round the sun, and moving, at the same time, in subordinate 

 orbits, round the primary planets. The earth is attended by the moon, 

 Jupiter by four moons or satellites, Saturn by seven, besides his ring, and 

 the Georgian planet by six moons. All these satellites move in the direct 



