

refractive and dispersive Powers of the Atmosphere, Sfc. 201 



coloured spectrum in the field of the glass. By the adapta- 

 tion of a more perfectly prismatic lens to the telescope, we get 

 a still more distinct spectrum, and are enabled to contemplate 

 the particular composition of light possessed by each star re- 

 spectively. I was not aware of the best means of detecting 

 these differences, till I read the excellent paper On the Disper- 

 sive Power of the Atmosphere, by Mr. Stephen Lee, published 

 in the Transactions of the Royal Society*. As some of my own 

 observations coincide with those detailed in the aforesaid paper, 

 I feel additional confidence in giving them to the public, as 

 the acuteness and ability of that gentleman as an astronomer 

 are well known. Mr. Lee viewed the stars through a prism 

 adapted to the eye glass of a reflecting telescope; and, 

 prompted by a laudable desire to ascertain how far the disper- 

 sive power of the atmosphere could pi'oduce an effect on astro- 

 nomical observations, he proceeded to examine several stars, 

 with a view to ascertain, if possible, the exact degree of se- 

 paration of the several rays. As the above paper ought to be 

 read by all observers, I shall not extract any of the observa- 

 tions now, but proceed to the subject under consideration,— 

 the varieties of stellar light. 



According to my observations, the stars should be classed 

 according to their colours, into the red, the yellow, the bril- 

 liant white, the dull white, and the anomalous. For though 

 each star may differ somewhat from every other, yet we shall 

 be assisted by this general classification. 



When observed with a prismatic glass as above described, 

 Sirius shows a large brush of extremely beautiful violet colour, 

 and, generally speaking, the most refrangible rays in great 

 quantity. The same applies more or less to all the bright 

 white stars. 



Procyon is far less beautiful than Sirius, and shows more of 

 the yellow colour. 



Aldebaran, together with many of the other red stars, exhi- 

 bits a very small proportion of the more refrangible colours. 



Arcturus much resembles Aldebaran, but differs in the lesser 

 proportion of the red to the other rays. 



Betalgeus is another red star, little inferior in magnitude 

 to the two above. This star shows also but little of the more 

 refrangible rays ; but the spectrum is always a bad one, and is 

 for some unknown cause more liable to fluctuation than the 

 above two. 



Antares, the most extraordinary star of all, contains, like 

 Aldebaran and Arcturus, much red light ; but owing to its 



* See Supplement. 

 Vol.63. No. 311. March 1824. C c greater 



