[ 542 ] 

 LXXIII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from p. 474.] 



November 15, 1866. — Lieutenant-General Sabine, President, in the 



Chair. 

 HHHE following communication was read : — 

 -*• "Spectroscopic Observations of the Sun." By J. Norman 

 Lockyer, F.R.A.S. 



The two most recent theories dealing with the physical constitu- 

 tion of the sun are due to M. Faye and to Messrs. De la Rue, 

 Balfour Stewart, and Loewy. The chief point of difference in these 

 two theories is the explanation given by each of the phenomena of 

 sun-spots. 



Thus, according to M. Faye *, the interior of the sun is a ne- 

 bulous gaseous mass of feeble radiating-power, at a temperature of 

 dissociation ; the photosphere is, on the other hand, of a high ra- 

 diating-power, and at a temperature sufficiently low to permit of 

 chemical action. In a sun-spot we see the interior nebulous mass 

 through an opening in the photosphere, caused by an upward current, 

 and the sun-spot is black, by reason of the feeble radiating-power 

 of the nebulous mass. 



In the theory held by Messrs. De la Rue, Stewart, and Loewy f, 

 the appearances connected with sun-spots are referred to the effects, 

 cooling and absorptive, of an inrush, or descending current, of the 

 sun's atmosphere, which is known to be colder than the photosphere. 



In June 1865 I communicated to the Royal Astronomical Society J 

 some observations (referred to by the authors last named) which 

 had led me independently to the same conclusion as the one an- 

 nounced by them. The observations indicated that, instead of a spot 

 being caused by an upward current, it is caused by a downward one, 

 and that the results, or, at all events, the concomitants of the down- 

 ward current are a dimming and possible vaporization of the cloud- 

 masses carried down. I was led to hold that the current had a 

 downward direction by the fact that one of the cloud-masses ob- 

 served passed in succession, in the space of about two hours, through 

 the various orders of brightness exhibited by faculce, general surface, 

 and penumbrce. 



On March 4th of the present year I commenced a spectroscopic 

 observation of sun-spots, with a view of endeavouring to test the 

 two rival theories, and especially of following up the observations 

 before alluded to. 



The method I adopted was to apply a direct-vision spectroscope to 

 my 6J-inch equatoreal (by Messrs. Cooke and Sons) at some distance 

 outside the eyepiece, with its axis coincident with the axis of the tele- 

 scope prolonged. In front of the slit of the spectroscope was placed 



* Comptes Eendus, vol. lx. pp. 89-138, abstracted in 'The Eeader,' 4th. 

 February, 1865. 



t Researches on Solar Physics. Printed for private circulation. Taylor 

 and Francis, 1865. 



\ Monthly Notices Roy. Ast. Soc. vol. xxv. p. 237. 



