OF ARTS AND SCIENCES. 179 



shadows projected upon the iiebuhi. I at iirst thought I Imd h;ft the 

 reticule of squares ruled on glass in the eye-piece ; but having convinced 

 myself that this was not so, and the same appearance again presenting 

 itself, I wiped my eye, but with no better result. As I experienced the 

 same thing on other nights, I paid no more attention to it, thinking the 

 trouble was in my sight. Some time afterwards, wliile in Washington, 

 I had an opportunity of studying the same nebula with tin; great 

 twenty-six-inch refractor of the Naval Observatory. I was not a little 

 surprised* to see that the ghost-like reticule which I wanted so much to 

 rub out of my eye while at home, was caused by dark channels in the 

 nebula itself, which is divided on the preceding side by bright luminous 

 patches, separated by dark intervals. 



In order of brightness, the zones or belts composing the system of 

 rings run as follows : C, Z), B, E, A, F; C being by far the brightest, 

 and F by fiir the darkest. The zones A and B have a bluish cast, or 

 light slate-color; Cis of a bright luminous white; D is shghtly gray- 

 ish ; ^ is at little darker ; while F, which is very dark, is tinged with 

 bluish purple. 



A is separated from B by the pencil line ; B from C by the principal 

 division ; while the others do not show any separation whatever, and 

 are only limited by the contrast of their different colors and shades, and 

 seem to be in immediate contact. However, the different zones do not 

 terminate abruptly where they come in contact, but seem somewhat 

 blended into each other. This is especially the case between E and 

 F. Though at that point the contrast between the two internal rings 

 is verj' great, yet it is impossible to see any line of division, so much 

 do they mingle at their point of contact. 



On good nights, I have often observed on that part of the rings A, B, 

 and C, seen on the ansse, an unmistakable mottled or cloudy appearance 

 such as is represented on Plate 1. This appearance was always more 

 characteristic and better seen on the ring G, especially near its outer 

 margin, close to the principal division. It would seem, as has been 

 already remarked, that the ring (7 is on a higher level than that of the 

 rest of tlie rings, and that the cloudy appearances observed there form 

 by their accumulation some kind of protuberances of different heights 

 and breadths. The bright spots resembling satellites, so often observed 

 by Bond in 1848, when the plane of the rings was parallel with that 

 of the ecliptic, were probably caused by the crests of some protuber- 

 ances similar to those now seen on the ansae. The form of the shadow 

 thrown by the planet on tlie rings on Nov. 30, 1874, as shown at x. 

 Fig. 1, seems also to agree with this hypothesis. The curious and deep 



