178 PROCEEDINGS OF THE AMERICAN ACADEMY 



with the foreshortening, and is soon lost. Probably I have never traced 

 it more than 30° or 40° on each side of the major axis of the rings. 

 The pencil line has never appeared to me black and well defined, but 

 rather grayish and diffused. Sometimes I have had the impression that 

 it was irregular in width and in depth of tint. 



These two lines are the only ones I have observed, which could, with 

 a certain amount of probability, be said to be a separation of the rings ; 

 though they might just as well be depressions, or dark belts, es{>ecially 

 the outer one. But the fact tiiat they have been observed on both sur- 

 faces north and south, apparently corresponding in position, is in favor 

 of their being real separations of the rings. Though I have repeatedly 

 endeavored to see the planet through the principal division between d 

 and e, Fig. 1, I have never seen the faintest traces of it; and I am 

 not aware that others have been more successful. 



If the principal division of the rings is, in fact, what it is said to be, — 

 viz., a space free from matter, and entirely disconnecting the rings B 

 and (7, — I do not see why the planet has never been seen through it. 

 If the planet could be seen through that space, the dark line forming 

 the principal division would be invisible from d to e, as the bright light 

 of the planet would shine through in its place, and be undistiiiguishable 

 from that of the rings. It may be objected that the invisibility of the 

 planet through the principal division is due to the thickness of the 

 ring G ; but, in this case, why should the black sky be seen, if the planet 

 is invisible ? 



Besides the two dark gaps or divisions of which I have just spoken, 

 the rings are subdivided by concentric zones or belts, which reflect light 

 of different hues and intensity. Though only three of these belts are 

 conspicuous, I have found by careful examination that there are six 

 which I can always recognize whenever tlie illumination is good, and 

 the image steady. These zones are represented on the diagram. Fig. 1, 

 at A, B, C, D, E, F. On several occasions, I have had a pretty dis- 

 tinct impression of seeing the whole surface, from C to E inclusive, 

 grooved, as it were, by numerous narrow concentric belts. These im- 

 pressioHo may have been illusory, as they were almost instantaneous ; 

 but I have since learned by experience, that, after all, rapid impressions 

 are not so much to be discarded, as, quite often, even nidre fugitive 

 impressions have proved in the end to be real. A striking instance 

 in my own experience may be worth recording. This Summer I 

 made a study of the Ilorse-shoe Nebula in Sagittarius with my 

 6|-inch refractor. During the course of my observations, I was 

 much annoyed by what appeared to me as faint ghost-like reticulated 



