72 ASTEONOMICAL TABLES. [SECT. vm. 



yond the reach of telescopic vision yet its mass, the form 

 and position of its orbit, and all the circumstances of its 

 motion may become known, and the limits of the solar 

 system may still be extended hundreds of millions of miles. 



The mean distance of Neptune from the sun has subse- 

 quently proved to be only 2450 millions of miles, and the 

 period of his revolution 166 years, so that Baron Bode's law, 

 of the interval between the orbits of any two planets being 

 twice as great as the inferior interval and half of the su- 

 perior, fails in the case of Neptune, though it was useful on 

 the first approximation to his motions ; and since Bode's 

 time it has led to the discovery of nine telescopic planets 

 revolving between the orbits of Mars and Jupiter, by chance ; 

 others by a systematic search on the faith that these minute 

 planets are fragments of a larger body that has exploded, 

 because their distances from the sun are nearly the same ; 

 the lines of the nodes of some of their orbits terminate in 

 the same points of the heavens, and the inclinations of their 

 orbits are such as might have taken place from their mu- 

 tual disturbances at the time of the explosion, and while 

 yet they were near enough for their forms to affect their 

 motions. 



The tables of Mars, Venus, and even those of the sun, 

 have been greatly improved, and still engage the attention 

 of the Astronomer Royal, Professor Airy, and other eminent 

 astronomers. We are chiefly indebted to the German astro- 

 nomers for tables of the four older telescopic planets, Vesta, 

 Juno, Ceres, and Pallas ; the other five have only been dis- 

 covered since the year 1845. 



The determination of the path of a planet when disturbed 

 by all the others, a problem which has employed the talents 

 of the greatest astronomers, from Newton to the present 

 day, was only successfully accomplished with regard to the 

 older planets, which revolve in nearly circular orbits, but 

 little inclined to the plane of the ecliptic. When the ex- 

 centricity and inclination of the orbits are great, their ana- 



