Another point for consideration is, that for a long time it was supposed, that the light emanating from any incandescent body always came to the eye as natural light, if in its passage it had not been reflected or refracted. But experiment by the polariscope shewed, that the ray departing from the surface at an angle sufficiently small was polarised; while at the same time, it was demonstrated that the light emitted by any gaseous body in flame--that of street-lamps, for instance--is always in the natural state, whatever be its angle of emission. From these remarks, some idea will be formed of the process necessary to prove whether the substance which renders the sun visible is solid, liquid, or gaseous. On looking at the sun in the polariscope, the image, as before observed, is seen to be purely white--a proof that the medium through which the luminous substance is made visible to us is gaseous. If it were liquid, the light would be coloured; and as regards solidity, that is out of the question--the rapid change of spots proves that the outer envelope of the sun is not solid. On whatever day of the year we examine, the light is always white. Thus, these experiments remove the theory out of the region of simple hypothesis, and give certainty to our conclusions respecting the photosphere.
Here an example occurs of the aids and confirmations which science may derive from apparently trivial circumstances. Complaint was made at a large warehouse in Paris, that the gas-fitters had thrown the light on the goods from the narrow, and not from the broad side of the flame. Experiments were instituted, which proved that the amount of light was the same whether emitted from the broad or narrow surface. It was shewn also, that a gaseous substance in flame appears more luminous when seen obliquely than perpendicular, which explains what are known as _faculæ_ and _lucules_, being those parts of the solar disk that shew themselves brighter than other portions of the surface. These are due to the presence of clouds in the solar atmosphere; the inclined portions of the clouds appearing brightest to the spectator. The notion, that there were thousands on thousands of points distinguishing themselves from the rest by a greater accumulation of luminous matter, is thus disposed of.