68 Royal Society : — 



5. We believe that the determination of the above-mentioned facts 

 leads us necessarily to several important modifications of the received 

 theory of the physical constitution of our central luminary — the 

 theory we owe to Kirchhoff, who based it upon his examination of 

 the solar spectrum. According to this hypothesis, the photosphere 

 itself is either solid or liquid, and it is surrounded by an atmosphere 

 composed of gases and the vapours of the substances incandescent in 

 the photosphere. 



We find, however, instead of this compound atmosphere, one 

 which gives us nearly, or at all events mainly the spectrum of hy- 

 drogen ; (it is not, however, composed necessarily of hydrogen alone ; 

 and this point is engaging our special attention ;) and the tenuity of 

 this incandescent atmosphere is such that it is extremely improbable 

 that any considerable atmosphere, such as the corona has been ima- 

 gined to indicate, lies outside it, — a view strengthened by the fact 

 that the chromosphere bright lines present no appearance of absorp- 

 tion, and that its physical conditions are not statical. 



With regard to the photosphere itself, so far from being either a 

 solid surface or a liquid ocean, that it is cloudy or gaseous or both 

 follows both from our observations and experiments. The separate 

 prior observations of both of us have shown : — 



i. That a gaseous condition of the photosphere is quite consistent 

 with its continuous spectrum. The possibility of this condition has 

 also been suggested by Messrs. De La Rue, Stewart, and Loewy. 



ii. That the spectrum of the photosphere contains bright lines 

 when the limb is observed, these bright lines indicating probably an 

 outer shell of the photosphere of a gaseous nature. 



hi. That a sun-spot is a region of greater absorption. 



iv. That occasionally photospheric matter appears to be injected 

 into the chromosphere. 



May not these facts indicate that the absorption to which the re- 

 versal of the spectrum and the Fraunhofer lines are due takes place 

 in the photosphere itself or extremely near to it, instead of in an ex- 

 tensive outer absorbing atmosphere ? And is not this conclusion 

 strengthened by the consideration that otherwise the newly disco- 

 vered bright lines in the solar spectrum itself should be themselves 

 reversed on Kirchhoff' s theory ? this, however, is not the case. We 

 do not forget that the selective radiation of the chromosphere does 

 not necessarily indicate the whole of its possible selective absorption ; 

 but our experiments lead us to believe that, were any considerable 

 quantity of metallic vapours present, their bright spectra would not 

 be entirely invisible in all strata of the chromosphere. 



February 18. — Lieut.- General Sabine, President, in the Chair. 



The following communication was read : — 



"Note on a Method of viewing the Solar Prominences without an 

 Eclipse." By William Huggins, F.R.S. 



Last Saturday, February 13, I succeeded in seeing a solar promi- 

 nence so as to distinguish its form. A spectroscope was used ; a 

 narrow slit was inserted after the train of prisms before the object- 

 glass of the little telescope. This slit limited the light entering the 



