Ffrm/iiion ef Planets from the S^lar Atmofphere, a\ 



" The atmofphere cannot extend itfelf at the equator to a greater diftance than to the 

 place where the centrifugal force is exa£lly equal to the force of gravity. With regard to 

 the fun, this point is remote from its centre to a diftance meafuring the radius of the 

 orbit of a planet which would make its revolution in the fame period as that luminary em- 

 ploys in its rotation. The filar atmofphere cannot therefore extend to the orbit of Mercury ; and 

 confequently it cannot produce the zodiacal light, which appears to extend even beyond 

 the orbit of the earth. 



" The point where the centrifugal force balances that of gravitation is nearer the body 

 the more rapid its rotation. If we conceive the atmofphere to extend as far as this lihiit, 

 and afterwards to contra£l and condenfe by cooling at the furface of the bcjdy, the motion 

 of rotation will become more and more rapid, and the extreme limit will continually ap- 

 proach towards the centre. The atmofphere will therefore fucceffively in the place of the 

 equator abandon zones of fluid, which will continue to circulate round the body, becaufe 

 their centrifugal force is equal to their gravity. But as this equality does not obtain with 

 regard to the parts of the atmofphere diftant from the equator, they will not ceafe to ap- 

 pertain to the planet. It is probable that the rings of Saturn are fimilar zones abandoned 

 by its atmofphere." (Vol. ii. p. 125.) 



" As the motions of the planets and their fatellltes are performed nearly in the fame 

 plane, we muft fuppofe one caufe to have adted on all thefe bodies ; and from the prodi- 

 gious diftances between them, it muft have been a fluid of immenfe extent. To have given 

 them in the fame direclion a motion, nearly circular, about the fun, it is necefl"ary that the 

 fluid muft have furrounded that ftar as an atmofphere. The confideration of the planetary 

 movements lead us therefore to think, that by virtue of an exceflive heat the atmofphere of 

 the fun was originally extended beyond the orbits of all the planets, and that it gradually 

 contra6led in procefs of time to its prefent limits. Thefe elfedts may have taken place 

 by caufes fimilar to that which occafioned the ftrong light for feveral months in the famous 

 flar which in the year 1572 appeared all at once in the conftellation of Caffiopeia. 



" The great eccentricity of the orbits of the comets leads to the fame refult. It evi- 

 dently indicates the difpofition of a great number of lefs eccentric orbits ; a circumftance 

 which fuppofes an atmofphere round the fun extending beyond the perihelia of the ob- 

 fervable comets, which, by deftroying the motions of thofe which happened to pafs within 

 it during the time of its greateft extent, united them to the body of the fun. Hence it 

 follows, that no other comets can at prefent be in exiftence, but fuch as were at that time 

 beyond that interval. And as we cannot obferve any comets but thofe which come near 

 the fun in their perihelium, their orbits muft be very eccentric. It alfo follows, that their 

 inclinations muft offer the fame irregularities as if thefe bodies had been projefted cafually ; 

 becaufe the folar atmofphere has not influenced their motions. The long time employed 

 by the comets in their revolutions, the great eccentricity of their orbits, and the variety of 

 their inclinations, are therefore very naturally explained by means of this atmofphere. 



••But in what manner have the movements of revolution and rotation of the planets been 

 cflTefted ? If thefe bodies had penetrated as fuch into the atmofphere of the fun, its refiftancc 

 muft have caufed them to fall to its furface. We may therefore conjefture that they were - 

 formed at the fucceffive limits of that atmofphere, by the condenfation of the zones which 

 it muft have abandoned in the plane of its equator during its cooling and condenfation at 

 Vol. II. — April 1798. G th« 



