NE-BUL.AR HYPOTHESIS. 



209 



then present the curious spectacle of planets revolving 

 at the same time on themselves and in their orbits. Fi- 

 nally, another very curious effect is also manifested in 

 these circumstances : besides three or four large spheres 

 into which the ring revolves itself, there are almost al- 

 ways produced one or two very small ones, which may 

 thus be compared to satellites. The experiment which 

 we have thus described presents, as we see, an image in 

 miniature of the formation of the planets, according to 

 ihe hypothesis of Laplace, by the rupture of the cosmical 

 rings attributable to the condensation of the solar atmo- 

 sphere."* 



Such illustrations certainly tend to take from the nebu- 

 lar cosmogony the character of a "splendid vision," 

 which one of my critics has applied to it. I may here 

 also remind the reader that there are other grounds for 

 this hypothesis, besides observations on the nebulae. 

 Overlooking the zodiacal light, which has been thought 

 a residuum ol tjie nebulous fluid of our system, we find 

 geology taking us back towards a state of our globe which 

 cannot otherwise be explained. It was clearly at one 

 time in a stateof igneous fluidity — the state in which its 

 oblately spheroidal form was assumed under the law of 

 centrifugal force. Since then it has cooled, at least in 

 the exterior crust. We thus have it passing through a 

 chemical process attended by diminishing heat. Whence 

 the heat at first, if not from the causes indicated in the 

 nebular hypothesis? But this is not all. In looking 

 back along the steps of such a process, we have no limit 

 imposed. There is nothing to call for our stopping till 

 ive reach one of those extreme temperatures which would 

 vaporize the solid materials ; and this gives us exactly 

 mat condition of things which is implied by the nebular 

 coomogony. 



Of particular objections it is not necessary to say much. 

 That there should be difficulties attending such a hypothe. 

 Bis is only to be expected ; but where general evidence ia 

 io strong, we should certainly be scrupulous about allow- 

 ing them too much weight. It is repiesented, for in- 

 itance, that the matter of the solar system could not, in 

 my conceivable gaseous form, fill the space comprehend- 



* Dr. Plateau on the Phenomena presented by a free Liquid 

 JIass withdrawn from the action of gravity. — Taylor's Scientific 

 Memoirs. November, 1844. 



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