Theory of the Constitution of the Sun. 91 



2v+l 

 16 



ah 



j(l-*+*— ■•) 



= -r-, *.&=—.' 1-2738. 



But if we calculate /> for this case from the previously derived 

 formula, it is found little different from this, namely 



= -i 1-2728, 

 ah 



XIII. A Theory of the Constitution of the Sun, founded upon 

 Spectroscopic Observations, original and other. By Charles 

 S. Hastings*. 



ERAUNHOFEK discovered the lines in the solar spec- 

 trum, known by his name, in 1814. Many efforts to 

 determine their origin followed. One of the most ingenious 

 and carefully considered was that of Professor Forbes, in 1836f . 

 He concluded that, if their origin is in the solar atmosphere, 

 the light from the limb must exhibit stronger lines than that 

 from the centre. His method was to examine the spectrum 

 before and during an annular eclipse ; as he found no recog- 

 nizable change, his deduction was " that the sun's atmosphere 

 has nothing to do with the production of this singular pheno- 

 menon." 



The point was again touched upon by Sir David Brewster 

 and Dr. Gladstone in a joint study of the spectral lines, pub- 

 lished in 1860$. Here " each of the authors came indepen- 

 dently to the conclusion that there is no perceptible difference 

 in this respect between the light from the edge and that from 

 the centre of the solar disk." 



In 1867 Angstrom § repeated the experiment with negative 

 results. Lockyer's|| efforts also, in 1869, were attended with 

 no better results. 



In 1873, four years later, I devised and made an apparatus 

 by which a perfect juxtaposition of the spectra of the centre 

 and limb was secured. This apparatus and certain of the 



* From Silliman's American JournaFof Science, January 1881. 

 t " Notes relative to the supposed Origin of the Deficient Eays in the 

 Solar Spectrum," Phil. Trans. 1836, pp. 453-456. 



t "On the Lines of the Solar Spectrum," Phil. Trans. I860, pp. 149-161. 

 § Phil. Mag. 1867, xxxiii. p. 76. || Proc. Roy. Soc. vol. xvii, p. 350. 



