M. Arago o?i the Physical Constitution of the Sun. 199 



Observations made any day of the year, looking directly at 

 the sun, with the aid of powerful polarizing telescopes, exhibit 

 no trace of colorization. The inflamed substance, then, which 

 defines the circumference of the sun, is gaseous. We can 

 generalize this conclusion, since, through the agency of rota- 

 tion, the different points of the surface of the sun come in 

 succession to form the circumference. 



This experiment removes out of the domain of simple hypo- . 

 thesis the theory we have previously indicated concerning the 

 constitution of the solar photosphere. We assuredly find, 

 neither in the arbitrary conceptions which are the results of 

 the brilliant imagination of the ancient philosophers of 

 Greece, nor in the extant works of the most celebrated 

 astronomers of the Alexandrian school, any thing which, 

 even by a forced assimilation, can be compared to the results 

 which I have just advanced. These results, let it be loudly 

 proclaimed, are entirely due to the united eff\:)rts of the 

 observers of the seventeenth and eighteenth centuries, and 

 also in a certain measure to those of our contemporary 

 astronomers. 



And here let me make a remark, which, when endea- 

 vouring to determine the physical constitution of the stars, 

 we shall have occasion to apply. 



If the material of the solar photosphere were liquid, if the 

 rays emitted from its margin were polarized, the two images 

 furnished by the polarizing telescope would not only be 

 coloured, but they would be different in the diff'erent parts of 

 the circumference. Is the highest point of one of these images 

 red, the point diametrically opposite will be red also. But 

 the two extremities of the horizontal diameter will each ex- 

 hibit a green tint, and so on. If, then, one succeeds in con- 



be observed, that the lights proceeding from two liquid substances, may, accord- 

 ing to the special nature of these substances, not be identical in reference to 

 the number and the position of the black bands of Fraunhofer, and which their 

 prismatic hues offer to the eye of tlie philosopher. 



These discrepancies are of a nature to be considerably augmented by the 

 dift'erently-constituted atmospheres through which the rays have to travel be- 

 fore reaching the observer.— (y^M note was not read at the jnibiic meeting of 

 the 25th of October.) 



