406 Mr. W. Huggins and Dr. W. A. Miller on the 



which, as the absence of sensible parallax in the case of most of 

 them shows, they must be placed from our system. 



The investigation of the nature of the fixed stars by a pris- 

 matic analysis of the light which comes to us from them r how- 

 ever, is surrounded with no ordinary difficulties. The light of 

 the bright stars, even when concentrated by an object-glass or 

 speculum, is found to become feeble when subjected to the large 

 amount of dispersion which is necessary to give certainty and 

 value to the comparison of the dark lines of the stellar spectra 

 with the bright lines of terrestrial matter. Another difficulty, 

 greater because it is in its effect upon observation more inju- 

 rious, and is altogether beyond the control of the experimen- 

 talist, presents itself in the ever-changing want of homogeneity 

 of the earth's atmosphere through which the stellar light has to 

 pass. This source of difficulty presses very heavily upon ob- 

 servers who have to work in a climate so unfavourable in this 

 respect as our own. On any but the finest nights the numerous 

 and closely approximated fine lines of the stellar spectra are seen 

 so fitfully that no observations of value can be made. It is from 

 this cause especially that we have found the inquiry, in which 

 for more than two years and a quarter we have been engaged, 

 more than usually toilsome ; and indeed it has demanded a sacri- 

 fice of time very great when compared with the amount of infor- 

 mation which we have been enabled to obtain. 



2. Previously to January 1862, in which month we commenced 

 these experiments, no results of any investigation undertaken 

 with a similar purpose had been published. With other objects 

 in view, two observers had described the spectra of a few of the 

 brighter stars, viz. Fraunhofer in 1823*, and Donati, whose 

 memoir, " Intorno alle strie degli spettri stellari," was published 

 in the Annali del Museo Florentine* for 1862. 



Fraunhofer recognized the solar lines D, E, b, and F in the 

 spectra of the Moon, Venus, and Mars ; he also found the line 

 I) in Capella, Betelgeux, Procyon, and Pollux; in the two former 

 he also mentions the presence of b. Castor and Sirius exhibited 

 other lines. Donates elaborate paper contains observations upon 

 fifteen stars; but in no case has he given the positions of more 

 than three or four bars, and the positions which he ascribes to 

 the lines of the different spectra relatively to the solar spectrum 

 do not accord with the results obtained either by Fraunhofer' or 

 by ourselves. As might have been anticipated from his well- 

 known accuracy, we have not found any error in the positions of 

 the lines indicated by Fraunhofer. 



3. Early in 1862 we had succeeded in arranging a form of 

 apparatus in which a few of the stronger lines in some of the 



* Gilbert's Annalen, vol. lxxiv. p. 374. 



