140 CLASSICS OF MODERN SCIENCE 

 ready observed, should be all very eccentric. The hypothesis, there- 

 fore, is far from satisfying the preceding phenomena. Let us con- 

 sider whether we can assign the true cause. 



Whatever may be its nature, since it has produced or influenced 

 the direction of the planetary motions, it must have embraced them 

 all within the sphere of its action ; and considering the immense 

 distance which intervenes between them, nothing could have effected 

 this but a fluid of almost indefinite extent. In order to have im- 

 pressed on them all a motion q. p. circular and in the same direction 

 about the Sun, this fluid must environ this star, like an atmosphere. 

 From a consideration of the planetary motions, we are therefore 

 brought to the conclusion, that in consequence of an excessive heat, 

 the solar atmosphere originally extended beyond the orbits of all 

 the planets, and that it has successively contracted itself within its 

 present limits. 



In the primitive state in which we have supposed the Sun to be, it 

 resembles those substances which are termed nebulae, which, when 

 seen through telescopes, appear to be composed of a nucleus, more or 

 less brilliant, surrounded by a nebulosity, which, by condensing on its 

 surface, transforms it into a star. If all the stars are conceived to be 

 similarly formed, we can suppose their anterior state of nebulosity 

 to be preceded by other states, in which the nebulous matter was more 

 or less diffuse, the nucleus being at the same time more or less 

 brilliant. By going back in this manner, we shall arrive at a state 

 of nebulosity so diffuse, that its existence can with difficulty be 

 conceived. 



For a considerable time back, the particular arrangement of some 

 stars visible to the naked eye, has engaged the attention of philos©- 

 phers. Mitchel remarked long since how extremely improbable it 

 was that the stars composing the constellation called the Pleiades, for 

 example, should be confined within the narrow space which contains 

 them, by the sole chance of hazard; from which he inferred that this 

 group of stars, and the similar groups which the heavens present to 

 us, are the effects of a primitive law of nature. These groups are 

 a general result of the condensation of nebulae of several nuclei ; for 

 it is evident that the nebulous matter being perpetually attracted by 

 these diff'erent nuclei, ought at length to form a group of stars, like 

 to that of the Pleiades. The condensation of nebulae consisting of 



