14 Wilde, Origin of Cometary Bodies and Saturn s Rings. 



The ejecta from this volcano reached a height of more 

 than 30 miles, forming a belt 20° wide on each side of the 

 equator, and made two successive revolutions round the 

 globe in the course of twenty-five days. The optical 

 phenomena attending the eruption also included blue, 

 green, and copper-coloured suns similar to the transient 

 colours observed on the belts of Jupiter. 



The problem of the origin of Saturn's rings has for a 

 long time engaged the attention of natural philosophers, 

 but no solution has yet been offered of sufficient im- 

 portance to gain the general assent of astronomers. The 

 first of these attempts was made in 1755 by Kant in his 

 " Natural History and Theory of the Heavens," wherein 

 he assumes that Saturn at an early period of its history 

 had the characteristics of a comet and moved in an orbit 

 of great eccentricity. That its tails gradually contracted 

 upon the planet to form a cometic atmosphere of vapours 

 which subsequently changed into the form of a ring 

 entirely separated from the body of the planet. 



In the " Systeme du Monde " of Laplace the rings are 

 supposed to be the original nebular substance uncon- 

 densed into the form of satellites. This opinion has since 

 been strongly held by astronomers and other scientific 

 investigators and utilised as an illustration of the nebular 

 theory of the origin of planetary systems. 



Recent spectroscopic and mathematical investigations 

 have, however, shown that the rings consist of a vast 

 number of minute bodies, in confirmation of the views 

 previously advanced by J. D. and J. Cassini in the 

 Memoirs of the F rend I Academy of Sciences in 1705 and 

 1715. 



In neither of the explanations of the origin of Saturn's 

 rings by Kant and Laplace is there any suggestion of the 



