90 COSMOS. 



tein tlie center of gravity is often co.Tipriseil within the inner" 

 most limits of a visible central body. If, therefore, we regard 

 the Sun and the Earth, or the Earth and the Moon, as double- 

 stars, and the whole of our planetary solar system as a multi- 

 ple cluster of stars, the analogy thus suggested must be limit- 

 ed to the universality of the laws of attraction in different sys- 

 tems, being alike applicable to the independent processes of 

 light and to the method of illumination. 



For the generalization of cosmical views, corresponding with 

 the plan we have proposed to follow in giving a delineation of 

 nature or of the universe, the solar system to which the Earth 

 belongs may be considered in a two-fold relation : first, with 

 respect to the different classes of individually agglom.erated 

 matter, and the relative size, conformation, density, and dis- 

 tance of the heavenly bodies of this system ; and, secondly, 

 with reference to other portions of our starry cluster, and oX 

 the changes of position of its central body, the Sun. 



The solar system, that is to say, the variously-formed matter 

 circling round the Sun, consists, according to the present state 

 of our knowledge, of eleven lorimary j)lcinet$* eighteen satel- 



* [Since the publication of Baron Humboldt's work in 1845, ses'eral 

 other planets have been discovered, making the number of those be- 

 longing to our planetaiy system sixteen instead of eleven. Of these, 

 Astrea, Hebe, Flora, and Iris are members of the remarkable group 

 of asteroids between Mars and Jupiter. Astrea and Hebe were dis- 

 covered by Hencke at Driesen, the one in 1846 and the other in 1847 ; 

 Flora and Iris were both discovered in 1847 by Mr. Hind, at the South 

 Villa Observatory, Regent's Park. It would appear from the latest de- 

 terminations of their elements, that the small planets have the following 

 order with respect to mean distance from the Sun : Flora, Iris, Vesta, 

 Hebe, Astrea, Juno, Ceres, Pallas. Of these, Flora has the shortest 

 period (about 3^ years). The planet Neptune, which, after having 

 been predicted by several astronomers, was actually observed on tho 

 25th of September, 1846, is situated on the confines of our planetary 

 system beyond Uranus. The discovery of this planet is not only highly 

 interesting from the importance attached to it as a question of science, 

 but also from the evidence it affords of the care and unremitting labor 

 evinced by modern astronomers in the investigation and comparison of 

 the older calculations, and the ingenious application of the results thus 

 obtained to the observation of new facts. The merit of having paved 

 the way for the discovery of the planet Neptune is due to M. Bouvard . 

 who, in his persevering and assiduous efforts to deduce the entire crbil 

 of Uranus from observations made during the forty years that succeed- 

 ed the discovery of that planet in 1781, found the results yielded by 

 theory to be at variance with fact, in a degree that had no parallel in 

 the history of astronomy. This startling discrepancy, wiiich seemed 

 only to gain additional weight from every attempt made by M. Bouvard 

 to correct his calculations, led Levei-riei", after a careful modification of 

 the tables of Bouvard. to establish the proposition that there was *' » 



