76 THE SUN. 



had access to the original papers containing this investigation, we can only 

 speak of it from the imperfect information supplied by that report. It would 

 seem from it that Arago reasons in the following manner : There are two 

 states in which light is capable of existing ; the ordinary state, and the state 

 of polarization. It has been proved by Fourier, that all bodies rendered in- 

 candescent by heat, which are in the solid or liquid state, emit polarized 

 light ; while bodies which are gaseous, when rendered incandescent, invariably 

 emit light in its ordinary state. Thus the physical condition of a body may 

 be distinguished when it is incandescent, by examining the light which it 

 affords. There are polariscopic instruments by which we are enabled to dis- 

 tinguish these different states of light. On applying these tests to the direct 

 light of the sun, it has been found to be in the unpolarized, or ordinary condi- 

 tion. Hence it has been inferred by Arago, that the matter from which this 

 light proceeds must be in the gaseous state. It will doubtless be readily un- 

 derstood that gas, when incandescent, is that which is commonly called flame. 

 If Arago's reasoning, then, be rightly reported, and his observations correct, 

 it follows that the globe of the sun is a solid, opaque, non-luminous orb, in- 

 vested with an ocean of flame. 



Certain observations made by Bouguer, led that astronomer to suppose that 

 the sun is surrounded by an atmosphere of considerable extent above the sur- 

 face of the luminous coating. The ground of this supposition was the impres- 

 sion that the splendor of the sun's light near the borders of the disk was less 

 than near the centre ; an effect which could not be produced if the luminous 

 coating had nothing above it imperfectly transparent. On the contrary, the 

 brightness toward the borders, owing to the obliquity of the direction of the 

 surface to the line of vision would be greater, inasmuch as a greater extent of 

 luminous, surface would be comprised within the same visual angle. The 

 more accurate observations, however, of Arago, made with delicate polariscopic 

 instruments disprove this by showing that the brightness is the same on all 

 parts of the sun's disk 



