182 PROCEEDINGS OF THE AMERICAN ACADEMY 



seems to prove that the planet is less luminous on its border than else- 

 where, providing the above explanation holds good ; and this may be 

 owing to the absorption caused by an atmosphere surrounding the 

 planet. 



Bond has represented the limb of the globe of Saturn as seen through 

 the whole width of the dusky ring. In this he agrees with all pre- 

 vious observers. All the drawings of Saturn represent the limb of tliis 

 jilanet as plainly and equally visible throughout tlie dusky ring, becom- 

 ing invisible only where it enters under tlie internal margin of the ring 

 E. In Bond's memoir, it is positively stated that Mr. Tuttle saw the 

 limb of the planet through the whole width of the dusky ring. If 

 these observations are correct, — as without doubt they are, — the solid 

 particles, vapors or gases, composing this ring, must have luidergone 

 some changes of position since Bond's time ; as by using tlie same 

 instrument, and even one of almost double the aperture, I have not 

 been able to confirm these observations. 



During the last four years, I have never been able to see the limb of 

 the planet Saturn under the dusky ring, beyond the middle of its 

 width. As it enters under it at m and p, it remains quite distinct for 

 a short distance : but, as it advances farther in, it diminishes gradually ; 

 and it entirely vanishes at about the middle, at u and v ; as if the matter 

 composing the dusky ring was more dense or thicker towards its outer 

 border. This observation has been so carefully made, and so many 

 times repeated, the phenomenon has been so distinctly seen, that there 

 is not the least doubt in my mind as to its reality. Therefore it seems 

 pretty certain that changes have lately taken place in the distribution 

 of the matter composing the dusky ring. 



As already shown, the substance composing the dusky ring does not 

 seem to be uniformly distributed ; but seems moreover to be agglome- 

 rated here and there into denser masses, which I have often recognized 

 upon that part of the dusky ring crossing the planet between u and 

 V. These supposed agglomerations appeared as dark masses, inter- 

 cepting the light of the planet. This phenomenon could not be attrib- 

 uted to dark markings on the planet, seen through the dusky ring ; 

 since there are no markings so dark and so small on Saturn. Neither 

 could they be produced by the dark bands sometimes surrounding the 

 globe of Saturn, as some traces would have been detected on the edge 

 of the dusky ring, since these bands are usually wider than the trans- 

 parent part of the dusky ring. 



Of the planet itself I have little to say. It has certainly a mottled 

 or cloudy appearance, like Jupiter. The clouds of Saturn are more 



