Cometary Bodies and Saturn's Rings. 751 



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 

 lime engaged the attention of natural philosophers, but no 

 solution has yet been offered of sufficient importance 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 uncondensed 

 into the form of satellites. This opinion has since been 

 strongly held by astronomers and other scientific investi- 

 gators, and utilized 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 

 French 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 

 interior of the planet as being the birthplace of these singular 

 appendages. It is therefore with some amount of diffidence 

 that I venture to affirm that they are the ejectamenta of 

 Saturn when its diminishing energies were insufficient to 

 eject a cometary satellite, or a comet with its train of meteo- 

 rites beyond the sphere of its gravitational attraction. And 

 here it may be well to remark that all meteoric and other 

 small discrete bodies are not formed directly from the 

 universal nebular substance, but are necessarily fragments 

 of the solid or liquid parts of a globe, which had a long- 

 previous history, involving the evolution of the several 

 series of elementary substances of which the globular body 

 was composed. 



The dimensions of Saturn's rings are drawn up in the 

 following table for a new determination of the times of their 



3 D 2 



