4 86 



NA TURE 



{March 26, 1885 



be generated. And, further, since we are favoured with 

 such a view of the polar regions as we can never obtain 

 on Jupiter, we may conjecture that the internal heat is 

 not great, or it would tend, by equalising the temperature 

 of the whole globe, to remove that difference of tint which 

 has been often remarked between the polar and more 

 temperate zones. But these are but guesses, and as such 

 they must remain. 



Then, as to the complex ring. Its constitution may be 

 deduced, within certain limits, from theoretical considera- 

 tions ; but it is beyond the power of observation to confirm 

 it. Especially as to the aspect of the dusky veil, if we 



accept the varied tints that have been ascribed to it in 

 opposite ansa;, it can hardly be said to correspond with 

 the idea of a thinly scattered stream of separate luminous 

 masses, and is still less capable — some would say incap- 

 able — of such an explanation where it is projected upon 

 the ball. The brighter ring gives no indication of its 

 structure, while showing from time to time marked varia- 

 tions in the relative light of its parts ; and of the period of 

 its rotation — pace Sir W. Herschel — there is no evidence 

 at all. Some observers have thought the great division 

 dusky, rather than black as it shows itself to others, and 

 the whole system of markings is stated to be occasionally 



unsymmetrical on the opposite sides of the planet — a very 

 perplexing anomaly ; for the only conceivable cause — a 

 perturbing influence uf the satellites— must be too feeble 

 to have any perceptible effect, even were they not all 

 drawing in different directions. 



This claims to be nothing more than a hasty and in- 

 complete notice of a subject of admitted difficulty. 

 Questions like these might easily be multiplied, especially 

 if we took into account such as arise at the time of the 

 edgewise presentation of the ring, its irregularity of illu- 

 mination, the probable want of parallelism between the 

 axis of the ring-system and that of the globe, the alleged 



" square-shouldered " outline, and similar peculiarities. 

 Nor has allusion been made to spectroscopic examina- 

 tion, which is stated to have detected the presence of 

 atmospheric bands and those of aqueous vapour, and may 

 possibly, as in the case of the sun, lead to results beyond 

 the bounds of telescopic research. If what has now been 

 said may serve to stimulate further and closer and more 

 systematic inquiry into this wonderful exhibition of 

 creative power, its purpose will have been attained. 



T. W. Webb 

 P.S.— May I be allowed to add that since the fore 

 going paper has been in the printer's hands, the kindness 



of M. Trouvelot has put me in possession of his yen 

 important observations of a recent date, proving that, as 

 far as he is personally concerned, there is no foundation 

 for the remarks which I have ventured to make as to 

 our comparative deficiency in progress. His careful and 

 multiplied observations from 1877 to 1884 have led him 

 to the conclusion that many anomalies, not otherwise to 

 be accounted for, must be due to actual variations in the 

 physical structure of the system. It would be a great 

 satisfaction to find that other observatories are likely to 

 prove as fruitful in valuable results as that of Meudon. 



I am permitted by the kindness of M. Flam- 

 marion to illustrate the present article by two very 

 effective woodcuts, which have appeared in his valu- 

 able and interesting periodical, V Astronomic, of which 

 he is now publishing an improved continuation. The 

 first exhibits the existing presentation of the ring 

 system in its fullest possible development ; the second, 

 the corresponding projection of the paths of the satel- 

 lites, in which, however, on account of its great extent, 

 the orbit of the outermost, Japetus, is unavoidably 

 omitted. T. W. W. 



