1863.] 445 



shows with considerable accuracy the principal lines which the 

 authors have seen in Sirius, Betelgeux, and Aldebaran, and their 

 position relatively to the chief solar lines. 



Without at present describing in detail, as they propose to do when 

 the experiments are completed, the arrangements of the special appa- 

 ratus employed, it may be sufficient to state that it is attached to an 

 achromatic telescope of 10 feet focal length, mounted in the observa- 

 tory of Mr. Huggins at Upper Tulse Hill. The object-glass, which 

 has an aperture of 8 inches, is a very fine one by Alvan Clark of 

 Cambridge, U.S. ; the equatorial mounting is by Cooke of York, and 

 the telescope is carried very smoothly by a clock motion. 



It may further be stated that the position in the stellar spectra 

 corresponding to that of Fraunhofer's line D, from which the others 

 are measured, has been obtained by coincidence with a sodium line, 

 the position of which in the apparatus was compared directly with the 

 line D in the solar spectrum. 



The lines in the drawings against which a mark is placed have 

 been measured. 



Addendum. Since the foregoing Note was presented to the 

 Royal Society, the authors have learned that a paper on the same 

 subject, accompanied by diagrams of the spectra of the Moon, 

 Jupiter, Mars, and several of the fixed stars, by Mr. L. M. Ruther- 

 furd, has appeared in the January Number of the f American Journal 

 of Science ' for the current year. The method of observing finally 

 employed by Mr. Rutherfurd much resembles that adopted by the 

 authors of this Note. 



They therefore desire to add that, during the past twelvemonth, 

 they have examined the spectra of the Moon, Jupiter, and Mars, as 

 well as of between thirty and forty stars, including those of Arcturus, 

 Castor, a Lyrse, Capella, and Procyon, some of the principal lines 

 of which they have measured approximative^. They have also 

 observed /3 and y Andromedse, a, /3, e and T\ Pegasi, Rigel, rj Orionis, 

 /3 Aurigse, Pollux, y Geminorum, a, y and e Cygni, a Trianguli, 

 e, and ?/ Ursse Majoris, a, /3, y, t and 17 Cassiopeiee, and some 

 others. [Feb. 21, 1863.] 



VOL. XII. 2 K 



