OF ARTS AND SCIENCES. 181 



may be the material of which this ring is composed, it is quite rarefied ; 

 and it becomes more and more so as it approaches its inner margin. 

 There, it seems to be composed of discrete particles, each of which 

 reflects the light separately ; and, by applying high powers to telescopes 

 of large aperture, I have had the impression that the supposed par- 

 ticles were more widely separated by the increase of magnifying power. 

 I do not pretend to have seen distinct and isolated particles in the 

 dusky ring ; but by instants my impressions have been so decided, that 

 it seemed as if only a little more favorable conditions were required to 

 enable me to see separate corpuscles of matter. The appearance was 

 somewhat like fine particles of dust floating in a ray of light traversing 

 a dark chamber. 



The inner border of the dusky ring, notwitlistanding its dark ap- 

 pearance, is sharply defined on the dark sky within the ansne ; but 

 it loses this sharpness of outline in that part which is seen projected 

 upon the disk of the planet. There it appears very diffused and ill 

 defined. 



The inner border of the dusky ring, as seen within the ansae, forms a 

 part of a perfect ellipse concentric with the other rings ; but these 

 graceful curves are remarkably and quite abruptly distorted where 

 they enter upon the disk of the planet at m audjt). Fig. 1. At these 

 points, they are seen turning up rapidly, describing a short curve ; after 

 which they continue parallel with the curves of the other rings until 

 they meet at h. If the ellipse described within the ansae should cross 

 the planet without any defiection, it would be seen along the dotted 

 line, Fig. 1, and pass through n; while, on the contrary, it is seen 

 above at h. 



I was quite surprised, at first, by this singular phenomenon ; but I at 

 last satisfied myself with the following explanation : If we conceive the 

 dusky ring to be made up either of vapors or of numerous small inde- 

 pendent solid bodies, and, moreover, if we conceive the thickness of 

 this ring as increasing from its interior margin to its outer limit, we 

 shall have an easy explanation of the observed phenomena. When 

 the matter composing this ring, whether solid or gaseous, is seen pro- 

 jected upon the disk of the planet brilliantly illuminated, it will be 

 lost, and will individually disappear, absorbed by the irradiation of the 

 bright light surrounding it, and it will remain visible only at that part 

 where it forms a stratum thick enough to overpower the eflfect of 

 irradiation. 



The fact that the distortion of the inner margin of the dusky ring is 

 not abrupt at w and p, where it enters upon the disk, but i? gradual^ 



