IV.] THE SUNS CHROMOSPHERE. 41 



This conclusion differs considerably from the opinion generally held. 

 In my paper on the eclipse of 1893,* I referred at length to this 

 point. The matter is so important that I do not hesitate to quote 

 what I then said. 



" As a result of solar spectroscopic observations, combined with 

 laboratory work, Dr. Frankland and myself came to the conclusion, 

 in 1869, that at least in one particular, Kirchhoff's theory of the 

 solar constitution required modification. In that year we wrote as 

 follows : f 



" ' May not these facts indicate that the absorption to which the 

 reversal of the spectrum and the Fraunhofer lines are due takes 

 place in the photosphere itself, or extremely near to it, instead of in 

 an extensive outer absorbing atmosphere ? ' 



"In an early observation of a prominence on April 17th, 1870, I 

 found hundreds of the Fraunhofer lines bright at the base, and 

 remarked that ' a more convincing proof of the theory of the solar 

 constitution put forward by Dr. Frankland and myself could scarcely 

 have been furnished.' J 



" During the eclipse of 1870, at the moment of disappearance of 

 the sun, a similar reversal of lines was noticed; we had, to quote 

 Professor Young, ' a sudden reversal into brightness and colour of 

 the countless dark lines of the spectrum at the commencement of 

 totality.' On these observations was based the view that there was a 

 region some 2"' high above the photosphere, which reversed for us all 

 the lines visible in the solar spectrum and on this ground the name 

 ' reversing layer ' was given to it. 



" Continued observations, however, led me, in 1873, to abandon 

 the view that the absorption phenomena of the solar spectrum are 

 produced by any such thin stratum, and convinced me that the absorp- 

 tion took place at various levels above the photosphere. I need not 

 give the evidence here ; it is set forth in my Chemistry of the Sun. 

 On the latter hypothesis the different vapours exist normally at 

 different distances above the photosphere according to their powers of 

 resisting the dissociating effects of heat.|j 



" My observations during the eclipse of 1882, in the seven minutes 

 preceding totality, to my mind set the matter at rest. * We begin with 

 one short and brilliant line constantly seen in prominences, never 

 seen in spots. Next another line appears, also constantly seen in 



* Phil. Trans., 1890, vol. clxxxvii, A, p. 603. 



f Proc. Soy. Sot., vol. xvii, p. 8S. 



J Ibid., vol. xviii, p. 353. 



Chapter XXII, pp. 303309. 



|j Proc. Hoy. Soc., vol. xxxiv, p. 292. 



