192 PROCEEDINGS OF THE AMERICAN ACADEMY 



From these observations, it would seem that this phenomenon is not a 

 very rare one ; but it is not permanent, as Professor Hall appears to 

 have supposed. 



I am indebted to Professor Edward S. Holden, of the Naval Obser- 

 vatory, for an interesting drawing and observation of Saturn, which he 

 made with the 28-inch silvered-glass reflector of Dr. Henry Draper 

 of New York, on the night of Sept. 8, 1874. At his request, Dr. 

 Draper has kindly sent to me a tracing of his original drawing, accom- 

 panied with the memorandum recorded in the note-book, at the moment 

 of the observation. It reads as follows : " Observation of Sept. 8, 1874. 

 Division of rings seen all round ; inner ring greatly brighter than 

 outer, particularly on the outer edge of it: main belt triple, reddish 

 brown in color; upper and lower edges of belt sharp. Shadow of 

 ball, on ring, like this ; i.e., funnel-shaped." Fig. 1, 

 As to the jagged appearance of the outer border 

 of the principal division, Professor Hall has seen no 

 trace of it. He says : " The only approach to the 

 appearance of the division as drawn by Mr. Trouve- 

 Fig. 1. lot that I have ever seen has been when the image 



of the planet was tremulous, and the sky so clear as to give a distinct 

 but unsteady view of the division of the Ring. At such times the 

 unsteady appearance of the division might lead to some such view 

 as that given by Mr. Trouvelot; but still I think he must have seen 

 something quite different." After saying that, during six or eight 

 nights in a year, their large telescope gives excellent images of Saturn, 

 he continues : " On these nights the appearance of the planet is very 

 beautiful ; but my experience is that on these rare nights one will see 

 fewer strange phenomena about the Ring and the shadows than when 

 the images are blurred and indistinct." 



Even if I could have been so greatly deceived as to represent for 

 realities the deformations undergone by images in rapid vibrations, I 

 am pretty certain that I could not have seen the delicate dark angular 

 forms which I have represented, but rather rounded, ill-defined forms 

 totally wanting in the blackness and sharpness of those which I saw. 

 Contrary to Professor Hall's suggestion, it is precisely when the defi- 

 nition was the most perfect that the " strange phenomena " could be 

 seen with more distinctness, and at the moment the image became trem- 

 ulous in the least, it disappeared confounded with the dark division of 

 the rings. 



The fact that Professor Hall has not been able to see the " Pencil 

 line," even during one of these beautiful nights he speaks of, sufficiently 



