PROGRESS OF MODERN ASTRONOMY 



of the planetary movements leads us then to think 

 that, on account of excessive heat, the atmosphere of 

 the sun originally extended beyond the orbits of all 

 the planets, and that it was successively contracted to 

 its present limits. 



" In the primitive condition in which we suppose the 

 sun to have been, it resembled a nebula such as the 

 telescope shows is composed of a nucleus more or less 

 brilliant, surrounded by a nebulosity which, on con- 

 densing itself towards the centre, forms a star. If it is 

 conceived by analogy that all the stars were formed in 

 this manner, it is possible to imagine their previous 

 condition of nebulosity, itself preceded by other states 

 in which the nebulous matter w r as still more diffused, 

 the nucleus being less and less luminous. By going 

 back as far as possible, we thus arrive at a nebulosity 

 so diffused that its existence could hardly be sus- 

 pected. 



" For a long time the peculiar disposition of certain 

 stars, visible to the unaided eye, has struck philo- 

 sophical observers. Mitchell has already remarked 

 how little probable it is that the stars in the Pleiades, 

 for example, could have been contracted into the small 

 space which encloses them by the fortuity of chance 

 alone, and he has concluded that this group of stars, 

 and similar groups which the skies present to us, are 

 the necessary result of the condensation of a nebula, 

 with several nuclei, and it is evident that a nebula, by 

 nunlly contracting towards these various nuclei, 

 ngth would form a group of stars similar to the 

 ides. The condensation of a nebula with two 

 nuclei would form a system of stars close together, 



35 



