The point next to be mentioned is still more decisive. When the dark ring was carefully examined with powerful telescopes during the ten years following its discovery by Bond, at which time it was most favourably placed for observation, it was observed that the outline of the planet could be seen across the entire breadth of the dark ring. All the observations agreed in this respect. It was, indeed, noticed by Dawes that outside the planet's disc the dark ring showed varieties of tint, its inner half being darker than its outer portion. Lassell, observing the planet under most favourable conditions with his two-feet mirror at Malta, could not perceive these varieties of tint, which therefore we may judge to have been either not permanent or very slightly marked. But, as I have said, all observers agreed that the outline of the planet could be seen athwart the entire width of the dark ring. Mr. Trouvelot, however, has found that during the last four years the planet has not been visible through the whole width of the dark ring, but only through the inner half of the ring's breadth. It appears, then, that either the inner portion is getting continually thinner and thinner--that is, the satellites composing it are becoming continually more sparsely strewn--or that the outer portion is becoming more compact, doubtless by receiving stray satellites from the interior of the inner bright ring. It is clear that in Saturn's ring-system, if not in the planet itself, mighty changes are still taking place. It may be that the rings are being so fashioned under the forces to which they are subjected as to be on their way to becoming changed into separate satellites, inner members of that system which at present consists of eight secondary planets. But, whatever may be the end towards which these changes are tending, we see processes of evolution taking place which may be regarded as typifying the more extensive and probably more energetic processes whereby the solar system itself reached its present condition. I ventured more than ten years ago, in the preface to my treatise upon the planet Saturn, to suggest the possibility 'that in the variations perceptibly proceeding in the Saturnian ring-system a key may one day be found to the law of development under which the solar system has reached its present condition.' This suggestion seems to me strikingly confirmed by the recent discoveries. The planet Saturn and its appendages, always interesting to astronomers, are found more than ever worthy of close investigation and scrutiny. We may here, as it were, seize nature in the act, and trace out the actual progress of developments which at present are matters rather of theory than of observation. VIII. _COMETS AS PORTENTS_