452 L. Trouveht — Physical Ohservations of Saturn. 



colors and shades, and seem to be in immediate contact. How- 

 ever, 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 U and F. Though at that 

 point the contrast between the two internal rings is very 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 ansae, 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 (7, especially near its outer margin, close to the princi- 

 pal division. It would seem, as has been already remarked, 

 that the ring (7 is on a higlner level than that of the rest of the 

 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 protuberances similar to those now seen on 

 the ans83. The form of the shadow thrown by the planet on 

 the rings on Nov. 30, 1874, as shown at jc, fig. 1, seems also to 

 agree with this hypothesis. The curious and deep indentation 

 of the shadow at a:, in that part where it it is projected on the 

 outer border of the ring C, is perfectly explained on the suppo- 

 sition that this part of the ring is on a higher level. The same 

 shadow, as it appeared projected on the rings B and A, also 

 clearly indicates that the plane of these zones is on a lower level. 



In order to find the shape of the surface of the rings from the 

 observation of the form of the shadow thrown by the planet, I 

 have experimented on a miniature representation of Saturn, 

 illuminated by a lamp occupying the position of the sun, while 

 my eye occupied the position of the earth. By successive trials 

 in altering the shape of the miniature rings, I have soon found 

 what must be the form of the rings in order to give to the 

 shadow the same appearance which had been observed on the 

 planet ; and the result agrees with the explanation already given. 



From the form of the shadow as it has appeared at difterent 

 times during the last four years, and from the experiment just 

 mentioned, it seems pretty clear to me, that, from the inner mar- 

 gin of the dusky ring F, the thickness gradually increases 

 until it reaches the extreme border of the ring C, where it gently 

 decreases, as indicated by the rounding of the shadow at this 

 point ; after which it sinks perpendicularly down, until it comes 

 even with the general level of the rings B and A. The shghtly 

 curved appearance of the shadow of the planet during the pres- 

 ent year, with its concavity turned towards its globe, also sup- 

 ports this hypothesis. 



