of the Atmosphere, and on the Peculiarities of the Stars. 337 



the prism to the telescope in the case of fixed stars, while in 

 the case of the planets this method will not enable us to se- 

 parate the light at all. 



4. That in rapid gyrations of the telescope, dark lines are 

 produced, which intervene between the several colours: so 

 that the circle appears broken, the several colours seem like 

 separate portions of a circle of the same size, closely ar- 

 ranged in the same orbit, and being separated from each 

 other by narrow dark spaces. 



5. That when this effect of the dark intervals between the 

 colours takes place, we always observe other narrow spaces of 

 intense white light, also interposed between the colours, and 

 bordering on the dark spaces. 



6. These dark spaces cannot be obtained distinctly from the 

 light of Arcturus, and only in a very slight degree from that of 

 Aldebaran and Betalgeus. 



The motion of the glass of the telescope through which 

 the light of the star passes, certainly produces the colour; and 

 this inclined me to think that the alternate colours before 

 noticed are produced by some motion in the atmosphere, as I 

 have hinted at in your Number for March, p. 198. 



Does the fact that Arcturus resembles the planets, in not 

 affording the colours in any great degree, afford grounds for 

 considering him as the nearest of the fixed stars, and that di- 

 stance of the stars is one cause of the disposition of the light 

 to be easily separated ? 



I intend to offer some observations on the effects of refrac- 

 tion and reflection combined, in a future Number. 



I have been at the trouble, lately, of comparing the declina- 

 tions of the thirteen stars of the above table, as given by seven 

 different observers ; and I find that, generally speaking, the 

 greatest differences of results have occurred in those stars 

 whose proportionate refrangibility is the greatest and the least ; 

 and that the differences of results have been the least in Capella 

 and those stars whose refrangibility is nearest to the mean*. 



P. S. 



* I noticed with great interest the observation of Prof. Bessel respecting 

 the habits of observing, as agreeing with whatMaskelyne recorded of his very 

 accurate assistant, who from August 1/95 began to set down the transits i" 

 of time later than hitherto, and continued to increase till he at length put 

 them down ^a." too late. This sudden alteration in the time of recording 

 observations has occurred before. The causes of it lie deep in the nature of 

 the mind itself, and, I believe, do not depend on the instruments, or on any 

 derangement of the apparatus. When, however, we speak, as we must do in 

 ordinary language, of such errors being in the mind, we say very little as to the 

 particular cause of them. Astronomers in general may not admit, but I am 

 persuaded those who are physiologists will be prepared to understand what 

 1 am going to say on this subject, which has long been in my mind. The 



Vol. 63. No. 313. May 1S24. U u «"-or 



