56 The Planet Saturn. 



This is more comprehensible when we take into account 

 the extraordinary thinness of the ring, assumed by him at 

 100 miles, but reduced by Bond to less than 40. With its 

 breadth of some 26,000 or 28,000 miles, it is very conceivable 

 that, as Mr. Maxwell has asserted, it would be "not only 

 plastic but semi-fluid under the forces it would experience/'' 

 even if it were made of iron ! The American theorists had 

 preferred the hypothesis of its consisting of a number of 

 streams of fluid a little denser than water ; and the supposition 

 has even been entertained, and might we believe be maintained 

 with some plausibility, that it is of a vaporous nature. The 

 fact is — and we think it would be most readily admitted as 

 such by those who have most closely examined the object — 

 that it is extremely difficult to form any idea of its real nature 

 from observation ; and so long as that is the case, it offers a 

 wide field for the admission of dissimilar theories. The exist- 

 ence of the inner dusky ring Mr. Proctor refers to thinner 

 strata of satellites, which have been detached by the attraction 

 of the globe from the more luminous mass, without ceasing to 

 circulate round it. But, whatever may be thought of this 

 speculation as applied to the bright rings, we must say that it 

 appears to us inadmissible here. Without laying too much 

 stress on the circumstance that the inner edge of the luminous 

 ring is usually much more clearly distinguished from its darker 

 neighbour than might be expected on that supposition, we 

 must think that the aspect of the dusky ring in front of the 

 ball is quite inconsistent with it. In such a position, the 

 existence of a thinly scattered stream of light-reflecting satel- 

 lites would be barely, if at all, perceptible in the most powerful 

 instruments, instead of its challenging the eye so distinctly, 

 even in smaller ones, as a dusky zone, that it has been some- 

 times even mistaken for the shadow of the bright ring. Mr. 

 Proctor's hypothesis would naturally be connected, as he has 

 shown, with such a decrease in the dimensions of the ring as 

 has been attempted to be proved by Otto Struve from a com- 

 parison of the older and more recent drawings and measure- 

 ments; but he has not adverted, as might have been expected, 

 to the circumstance that in consequence of the very careful 

 investigation of Mr. Main, Struve's result has not received 

 the general concurrence of, at least, the astronomers of 

 England. 



We might enter into further detail, but this may suffice. 

 Our readers will have inferred our conclusion, that, notwith- 

 standing much diligent study and praiseworthy labour, the 

 subject is still not exhausted, and requires, as it deserves, to 

 receive a more extended elucidation. But for this it will be 

 better to wait till future observation has supplied more satis- 



