SPECIAL RESULTS IN THE URANOLOGICAL 



remote than the aphelia of Saturn, of Uranus, or of Neptune. 

 In a cosmical presentation or description of the Universe, 

 it is right to recall this variety or diversity between different 

 members of the solar system, which, however, by no means 

 excludes uniformity of origin and permanent dependence on 

 the same motive forces. 



Great as is still the obscurity which surrounds the mate- 

 rial or physical cause of the Zodiacal Light, yet, considering the 

 mathematical certainty that the limits of the Sun's atmosphere 

 cannot extend beyond -fa of the distance of Mercury, the 

 opinion contended for by Laplace, Schubert, Arago, Poisson, 

 and Biot, according to which the Zodiacal Light is sup- 

 posed to proceed from a detached, vaporous, flattened ring, 

 revolving freely in space between the orbits of Venus and 

 Mars, would seem the most satisfactory hypothesis which 

 presents itself in the present very defective state of our 

 knowledge. In the Sun, as well as in Saturn (a subordi- 

 nate system), the outermost limit of the atmosphere can 

 only extend to where the attraction of the central body 

 (whether primary or secondary) exactly balances the centri- 

 fugal force : the portions of the atmosphere which may have 

 passed beyond this limit become detached, and must pursue 

 their course either condensed into spheroidal planets or 

 satellites, or, if not in the form of spheres, in that of solid 

 or of vaporous rings. According to this view, the " Eing 

 of the Zodiacal Light" would take its place in the category 

 of planetary forms, subject to the general laws of their for- 

 mation. 



Erom the small progress in respect to observation which 

 has been made in this neglected part of our astronomical 



