414 
ME. W. HUG-GINS AND DE. W. A. MILLEE ON 
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 sacrifice of time very great when compared with 
the amount of information 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 Fiorentino 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 D in Capella, Betelgeux, Procyon, and Pollux ; 
in the two former he also mentions the presence of b. Castor and Sirius exhibited 
other lines. Donati’s 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 brighter stars could be seen. The remeasuring of 
those already described by Fraunhofer and Donati, and even the determining the 
positions of a few similar lines in other stars, however, would have been of little value 
for our special object, which was to ascertain, if possible, the constituent elements of the 
different stars. We therefore devoted considerable time and attention to the perfecting 
of an apparatus which should possess sufficient dispersive and defining power to resolve 
such lines as D and b of the solar spectrum. Such an instrument would bring out the 
finer lines of the spectra of the stars, if in this respect they resembled the sun. It was 
necessary for our purpose that the apparatus should further be adapted to give accurate 
measures of the lines which should be observed, and that it should also be so con- 
structed as to permit the spectra of the chemical elements to be observed in the instru- 
ment simultaneously with the spectra of the stars. In addition to this, it was needful 
that these two spectra should occupy such a position relatively to each other, as to 
enable the observer to determine with certainty the coincidence or non-coincidence of 
the bright lines of the elements with the dark lines in the light from the star. 
Before the end of the year 1862 we had succeeded in constructing an apparatus which 
fulfilled part of these conditions. With this some of the lines of the spectra of Alde- 
baran, a Orionis, and Sirius were- measured ; and from these measures diagrams of these 
stars, in greater detail than had then been published, were laid before the Royal Society 
in February 1863. After the note was sent to the Society, we became acquainted with 
some similar observations on several other stars by Rutherfurd, in Silliman’s Journal 
* Gilbert’s ‘ Ann a, Ian/ vol. Ixxiv. p. 374. 
