152 ANNUAL OF SCIENTIFIC DISCOVERY. 



white, or present all the colors of the spectrum. In that case a 

 motion appears to take place in their interior, which cannot be com- 

 pared with anything better than that of a liquid circulating with dif- 

 ficulty in narrow channels, in which it meets with obstacles. There 

 are also seen irregular concentric rings, which appear to move from 

 their common centre. Whatever may be the circumstances in which 

 the observer places himself, and whatever may be the precautions 

 which are taken to obviate the complication of the phenomenon, the 

 rays do not appear disposed as those in a circle ; they have not all a 

 common center, but form entangled bundles in a very peculiar manner. 

 At first sight I was struck with the resemblance which appeared to 

 me to exist between the arrangement of these rays and that of the 

 fibers of the crystalline lens ; and I attempted immediately some ex- 

 periments directed from that point of view. From among those 

 which I have made I will quote the two following, which, if they do 

 not prove that this apparent radiation is to be attributed to the crys- 

 talline lens, at least show completely that the phenomenon takes 

 place in the eye, and depends upon the structure of that organ. 



1. On looking at an image of the sun, produced in the circum- 

 stances above described, through a black screen, with a circular open- 

 ing of five or six millims. diameter, the image is seen upon the sur- 

 face which reflects it ; while the rays are separated from it and appear to 

 be super-imposed upon the screen, and this even when it is brought 

 very near the eye. 



2. If the head is inclined to the right or the left, the want of 

 symmetry which is observed in the arrangement of the rays follows 

 the movement of the eye, which under those circumstances turns up- 

 on its axis in the direction in which the head is inclined. M. Baud- 

 rimont, Comptes Rendus. 



ON TWINKLING. 



The following paper, from the " Annuaire du Bureau des Longi- 

 tudes,' 1852, one of the last that issued from the pen of M. Arago, has 

 been translated and published in the ' Proceedings of the Astronomi- 

 cal Society." M. Arago commences his inquiry by giving an exact 

 definition of the term scintillation. It is, he remarks, from not adopt- 

 ing a similar practice that astronomers and other physical inquirers 

 have hitherto failed to arrive at a satisfactory explanation of the 

 phenomenon. He affirms then that, in so far as naked-eye observers 

 of the heavens are concerned, scintillation, or twinkling, consists in 

 very rapid fluctuations in the brightness of the stars. These changes 

 are almost always accompanied by variations of color and certain 

 secondary effects, which are the immediate consequences of every 

 increase or diminution of brightness ; such as considerable alterations 

 in the apparent magnitudes of the stars, and in the length of the 

 diverging rays, which appear to issue in different directions from their 

 centers. It has been remarked from a very early age that the phe- 

 nomenon of twinkling is accompanied by a change of color. M. 



