88 



NATURE 



{Nov. 27, 1879 



the poles, announced by Herschel I. as the result of many 

 observations in 1805, has never been very satisfactorily 

 explained. It might have been discarded as an illusion 

 resulting from the crossing of the outlines of the globe 

 and rings, had it not been confirmed by repeated measure- 

 ment at the time. It is considered to have been subse- 

 quently disproved by a repetition of that process in other 

 hands ; but it does not appear that the latter measures 

 were taken at a time when the alleged deception existed. 

 An experiment might be tried of placing at a distance 

 from the eye (or better, the telescope, to insure perfectly 

 similar conditions) a transparency copied from Herschel's 

 figure, but with an elliptical, instead of " square- 

 shouldered," outline ; but even if, under any varied 

 illumination, the deception should recur, his measures 

 would still have to be accounted for, which do not seem 

 to have been affected by any imperfection in his 

 micrometer. 



But however this apparent anomaly maybe disposed of, 

 we are brought face to face, in the ring-system, with phe- 

 nomena unexampled, as far as our sight can reach, though 

 there may be thousands of them, and of still stranger 

 thing, in the depths of infinity. The minor peculiarities 

 of this complex arrangement are at present not readily 

 traceable in so foreshortened a projection, and some of 

 them would require instruments of great light and power; 

 but the gauzy portion of the slowly-opening ring is already 

 within the reach of moderate apertures. On many 

 accounts these marvellous features deserve an increasing 

 degree of scrutiny as the opportunities for it are becom- 

 ing more and more favourable ; and we may yet gain a 

 further insight into their structure. Still we must not 

 expect too much. Even should the bright rings be, 

 according to the prevalent opinion, a closely-packed mass 

 of satellites, we can hardly suppose it to be " resolvable " 

 with any future increase of optical power. Theory, 

 indeed, pronounces against a solid or even fluid composi- 

 tion; but the confident application of theory may possibly 



prove hazardous where materials wholly unknown may be 

 dominated by polar forces of unexplored intensity. It 

 may, indeed, be still an open question whether the aspect 

 of the dusky ring, especially as projected across the ball, 

 can be reconciled with the idea of a thin and scattered 

 stream of satellites, an idea that perhaps would never have 

 occurred to any actual observer, and that seems only a 

 theoretical consequence of the supposed constitution of 

 the other rings. Many questions, in fact, remain open, in 

 this system of wonders ; whether its general dimensions, 

 or the proportions of its several parts, are unchangeable ; 

 whether minor divisions can always, or ever, be estab- 

 lished ; whether the gauze ring is distinctly separated 

 from its neighbour; whether its colour is invariable; 

 whether a similar material glazes over, so to speak, the 

 great division of the two bright rings ; whether any 

 plausible explanation can ever be attempted of the 

 extraordinary outlines of the shadow of the globe upon 

 the outer ring, consistent with a thinness edgeways almost 

 invisible. There may well be " more things " here " than 

 are dreamt of in our philosophy." And in respect of the 

 general idea of possible changes, it is but fair to bear in 

 mind that our knowledge of this planet is confined to a 

 relatively short period, as compared with his annual 

 revolution. Only some seven Saturn ian summers and as 

 many winters have been exercising their influence on that 

 peculiarly delicate and complicated system since the first 

 employment of telescopic investigation— far less time 

 since the commencement of minute scrutiny. And in 

 addition to this the excentricity of the orbit is sufficient 

 to vary the amount of solar radiation at different periods 

 of his year, much more than is the case with our own 

 globe. 



It should not be forgotten, too, that the rotation of the 

 ring has hitherto been deduced from theory alone, and 

 ought, if possible, to be determined by observation ; 

 though where Herschel I. has failed, and Bond has not 

 succeeded, there may not be a very bright prospect for 

 subsequent observers. 



The satellites are interesting in many respects ; among 

 others they afford a curious instance of the diversity of 

 detail with unity of idea already alluded to. In our own 

 case the attendant bears so large a proportion to its 

 primary that Earth and Moon have been compared to a 

 double planet. Next, in Mars, we find a ratio of the 

 most opposite description. In Jupiter an intermediate 

 proportion exists between the primary and secondaries, 

 while the latter do not differ in magnitude very widely 

 among themselves. In Saturn we have an extension and 

 combination of the previous systems, not only in number 

 but in character ; extreme minuteness in several being 

 found in juxtaposition with considerable bulk in one of 

 the attendants. The striking irregularity of their sequence 

 in point of magnitude is a fresh exemplification of the 

 deviation from uniformity already referred to as so gene- 

 rally, and indeed almost universally, observable in the 

 solar system. It may be noted among the retinue of 

 Jupiter, where the largest is not the outermost of the 

 satellites ; but it is still more observable in the more 

 complicated arrangement of the satellites of Saturn. 

 The smallest in a general sense range nearest to the pri- 

 mary, yet the largest is not the most distant ; and next in 

 position to him comes the most minute of all. On the 

 same principle it is highly unlikely that the regular pro- 

 gression 1, 2, 4, 8 should express the real number of the 

 satellites attending respectively on the Earth, Mars, 

 Jupiter, and Saturn. More, probably, own the control 

 of the latter, and may be reserved as a triumph for Mr. 

 Common's magnificent 37-inch mirror which the spirited 

 possessor fully deserves. 



The well-known fact that the difficulty in detecting 

 objects of this nature diminishes as they become more 

 familiar, is well exemplified in these minute points. 

 Enceladus, once considered as suitable only for great 



