'i4Q PfiOCEEDINGS OP THE AMEIUCAN ACADEMY 



iNVEsnSAHCiNS on Light and Heat, made and published wholly or in part with appropriation 

 from the Rumford Fund. 



VII. 



A THEORY OF THE CONSTITUTION OF THE SUN, 

 FOUNDED UPON SPECTEOSCOPIC OBSERVATIONS, 

 ORIGINAL AND OTHER. 



By Chakles S. Hastings. 



Presented Oct. 13, 1880. 



Fraunhoper discovered the lines in the solar spectrum, known by 

 his name, in 1814. Many efforts to determine their origin followed. 

 One of the most ingenious and carefully considered was that of Pro- 

 fessor Forbes in 1836.* 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 recognizable 

 change, his deduction was, " that the sun's atmosphere has nothing to 

 do with the production of this singular phenomenon." 



The point was again touched upon by Sir David Brewster and Dr. 

 Gladstone in a joint study of the spectral lines, published in 1860.t 

 Here '^ each of the authors came independently 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 t 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 results gained by its 

 use were described in a note " On a Comparison of the Spectra of the 

 Limb and the Centre of the Sun," published in the American Journal 

 of Science, (1873,) Vol. V. pp. 369-371. I was then a student at 



* Note relative to the supposed Origin of the Deficient Rays in the Solar 

 Spectrum. Pliil. Trans., 1836, pp. 453-456. 



+ On the Lines of the Solar Spectrum. Phil. Trans., 1860, pp. 149-161. 

 t Phil. Mag., 1867, p. 76. 

 § Proc. R. S., xvii. 350. 



