less metal lead, deleterious in its influence on the body, and of little intrinsic value. The astrologers selected him as the planet working the most mischievous effects on the fortunes of the human race. He was held to be not only a mean but an evil planet, aptly named after the old time-god, whose cruelty was matched by his dullness and stupidity.

How different is all this to the reality! We turn on Saturn a powerful telescope on some calm clear night, when the air is well suited for observation, and we see the most beautiful picture conceivable-a glorious orb, the surface resplendent with the most beautiful colours, blue at the poles, yellow elsewhere, crossed by a creamy white central belt, and flecked with spots which under favourable circumstances show brown, and purple, and ruddy tints. The most wonderful part of the picture, however, is the amazing ring-system, not a mere ring as it is so often shown, but a complex system of rings, each curiously variegated in colour, while the innermost (richly purple under favourable observing conditions) is unique among celestial objects in being transparent, so that the orb of the planet can be seen through this crape veil ring,' as astronomers have called it.

The return of Saturn to our midnight skies presents a favourable opportunity for an enquiry into what has been learned respecting this beautiful planet, the most complex in construction of all the members of the solar system, inferior only to Jupiter in dimensions and mass,

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while surpassing even that prince of planets in the extent and importance of the scheme over which it bears sway. I shall proceed in this enquiry on the plan which I have heretofore adopted in these pages-not restricting my remarks to the mere physical wonders of the object dealt with, but endeavouring to present my subject in such a way as to indicate something of the purposes which Saturn may be supposed to fulfil in the scheme of creation. I shall be unable indeed to proceed so far in this direction as I should wish, or as some readers may expect. indeed I hold that many writers who, with an excellent purpose in view, have attempted to show forth the Creator's praise by indicating the plans He had in view when this or that arrangement in the universe was designed, have erred, mistaking their conviction that God worketh all things according to law,' for the power of ascertaining what that law may be. Yet it seems a useful and judicious exercise of the reason to endeavour to ascertain, where possible, the special purpose which various created things subserve in the economy of the universe.

Let us first picture to ourselves the wonderful dimensions of the ringed planet. He has a somewhat flattened globe, whose mean diameter is about 9 times that of the earth, so that his surface exceeds hers about 81 times, while his volume exceeds hers more than 700 times. But his mass does not exceed the earth's mass to so enormous a degree. For, regarding him as a whole,

his mean density is less than that of any known planet, being less than a seventh of the earth's, so that he exceeds her in mass only about 90 times instead of 700 times. But even this is still a very great disproportion; and, in fact, if all the planets except Jupiter were formed into a single mass, this mass would be little more than a third of Saturn's.

The globe of Saturn seems to be enwrapped within a dense cloud-laden atmosphere, resembling in many respects that which surrounds the planet Jupiter. In fact, for anything which is certainly known, Saturn may have no solid globe at all; for nothing fixed has ever been recognised in Saturn. We see an orb so enwrapped in cloud that all we can perceive, even when the outermost cloud layers pass away from any part of the disc, is an inner cloud envelope, which, for anything we know to the contrary, may not be the innermost. Indeed, one is perplexed, in enquiring into Saturn's deep and apparently dense atmosphere, by the difficulty of understanding how that atmosphere can possibly endure the enormous attraction to which we know it to be subjected. There is the attracting mass of Saturn drawing that atmosphere always down towards the planet's surface (if it has a surface) with such force that if much deeper than ours the atmosphere would actually be compressed into the liquid or solid form.

But there is another singular circumstance closely related to the one just mentioned. We might expect

that the enormous globe of Saturn, containing ninety times as much matter as the earth, would be greatly compressed by the attraction of its own parts on each other. For when we say that his mass exceeds the earth's ninety-fold, we in fact imply that his attractive energy, his might as a ruler of matter, exceeds the earth's in that degree. And what draws the earth's globe together, and compresses its inner parts to their present degree of density, is the attractive energy of its mass; so that we might expect the inner parts of Saturn to be compressed in proportion to his much greater mass, and his density consequently much greater. But, as I have said, his density is less than a seventh of the earth's.

How is it, then, that on the one hand Saturn's atmosphere is so deep and yet so mobile as we perceive it to be, while his mean density is less than that of water? This is a question of great importance in connection with the question of Saturn's habitability. For when all the circumstances are carefully considered, no way of removing the difficulty is recognised, except the supposition that the density of Saturn remains small and his atmosphere remains mobile by reason of an intense heat pervading the whole of Saturn's mass. We know of no power except heat which could prevent the enormous mass of Saturn from producing the effects due to its gravitating energy. We see in the sun's globe an illustration of the power which heat possesses in this respect. The sun's mass exceeds the earth's not ninety times, but three hundred

and fifteen thousand times, and yet his mean density is less than one-fourth of hers. But his fiery heat enables us to understand this circumstance. It vaporises the materials which we regard as the most stable, and expands the vapours thus produced. It swells the whole bulk of the sun, reducing his mean density not only below the density due to his enormous mass, but even below that due to a mass such as our earth's.

Saturn, however, does not, like the sun, show manifest signs of being pervaded by an intense heat. He does not glow with inherent light; and if he emits (as the supposition we are dealing with requires) an intense heat, the distance at which we are placed from him prevents us from becoming sensible of the fact. It is clear, of course, that he is not nearly so hot as the sun; and obviously we should not expect this, since his mass is but the 3,500th part of the sun's, while his density is more than half as great as the sun's. It would suffice to account for Saturn's actual density, if he is so hot only that although his real globe is glowing with the intensity of his heat, his atmosphere is non-luminous and loaded, moreover, with opaque clouds thrown up from the heated mass within. In this case he would appear much brighter than he would if his visible surface were like our white sandstone, for the clouds in his atmosphere would reflect much more light than any kind of earth known to us, shining, in fact, with a whiteness nearly equal to that of driven snow. And probably a certain quantity of the light from his glowing