THE SPIRAL NEBUI.^. ^ 



By P. PuiSEUX, 

 Men^her of the Academy of iSeiences, Professor at the Sorhonne, Astronomer at the Paris 



Observatory. 



The people whom we clami as our du-ect intellectual ancestors 

 wished to find nothing in the sky but spherical forms and circular 

 movements. The Greeks, lovers of an exact geometry, the Latins, 

 enamored of order and logic, took pleasure in simple combinations. 

 They would not willingly admit into the celestial throng clouds of 

 indefinite and complicated form. vSuch indefinite forms must belong 

 to the sublunar world. Comets, with their hairy aspect, passed 

 as meteors, taking their birth and vanishmg within our atmosphere. 

 In the Milky Way some saw an accidental derogation of the uni- 

 versal order or the trace of an imperfect joining of the two halves 

 of the celestial sphere. Others guessed it to be a mass of number- 

 less stars, too small and too distant to be separately seen. There 

 was no need, indeed no possibilty, of searching further. To those 

 whom the idea of sometliing beyond troubled, the existence of an 

 empyrean was conceded, a luminous region situated beyond the 

 stars, to which only those had access whose souls had become freed 

 from the bonds of flesh. 



But astronomy, no more than the other physical sciences, has 

 kept withm the bonds with which she was fettered in the name of 

 philosophy. No sooner was the telescope invented than several 

 observers used it to explore the sky. Then, as had been foreseen, 

 the Milky Way was resolved almost entirely into separate luminous 

 points. But, it is true, there were found a few refractory places, 

 where the diffused whiteness persisted in filling the field of the tele- 

 scope. Even outside the limits of the Milky Way, several such 

 masses, more or less perceptible to the naked eye, refused to be 

 decomposed. Simon Marius, in 1612, noted the great nebula of 

 Andromeda, which suggested to him the comparison, somewhat 

 trivial yet suggestive, of the flame of a candle seen through horn. 

 This pale glow, watched for many years, seems to rest absolutely 



1 Address delivered before the .Soui6t6 des Amis de rUuiwrst^, Feb. 1, VA2. TrausUiled by permis- 

 sion from Revue Siientifiqiie, Paris, Apr. 0, 1912, pp. 417-422. 



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