THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



DECEMBER 1860. 



LV. On the Form of Satellites revolving at small distances from 

 their Primaries, By Daniel Vaughan*. 



SECONDARY planets which revolve at comparatively small 

 distances from great central orbs, experience very singular 

 effects from a kind of disturbing action, which is either wholly 

 imperceptible on the primaries themselves, or is only manifested 

 in producing an alternate rise and fall of their extensive oceans. 

 The powerful attraction of Jupiter must cause his nearest satel- 

 lite to feel a tidal force several thousand times greater than that 

 which every day swells our terrestrial waters ; and the variation 

 of gravity on the surface of the small world, from this disturb- 

 ance alone, may be estimated as nearly five times as great as our 

 own globe exhibits in consequence of its diurnal movement. 

 In the Saturnian system, where many attendants are much closer 

 to the primary, they must be more seriously affected by its un- 

 equal attraction on their parts. Were the size of the orbit below 

 a certain limit, the disturbing influence of the central body would 

 so far neutralize the attractive power of the satellite in two direc- 

 tions as to render it incapable of maintaining the usual planetary 

 form; and it appears that, in the zone occupied by Saturn's 

 rings, no large secondary planets could roll in security unless 

 they were considerably more dense than the kind of matter 

 which predominates in that part of the solar domain. During 

 the year 1853, in announcing the result of my researches on this 

 subject, I ascribed the existence of the rings to their proximity 

 to Saturn ; and, though the theory has been slow in receiving 

 attention, I hope that it may now claim a degree of interest 

 sufficient to justify me in submitting to scientilic men, in the 



* Communicated by the Author. 

 Phil. Mag. S. 4. Vol. 20. No. 135. Dec. 1860. 2 E 



