star depths surrounding it. We are so in the habit of regarding the visible half-sphere of the heavens as a star canopy, at night, over the seemingly level earth, that it is difficult to conceive the complete starlit sphere within which each of the members of the sun's family really travels. And how wonderful must be the aspect of our sun seen from the interplanetary spaces without the intervention of that atmosphere of ours which veils his glories! The coloured prominences, and the deeply-hued sierra, would be clearly visible from such a standpoint, while around all would be seen the glorious corona with its complicated structure branching outwards into space, and, perhaps, mingling with the softer lustre of that immense disc of scattered matter which astronomers call the zodiacal light.

As our comet travelled towards the level in which the planets move, it was exposed to a new form of danger. Between the paths of Mars and Jupiter lies the zone of small planets. It is probable that there are myriads of these bodies of all orders of magnitude from the largestVesta, Juno, and the others first discovered to bodies perhaps as minute as the least of the meteors. Astronomers have already discovered 130 of these small planets, and continue yearly to discover more, while it is probable that the smaller members of the family will for ever remain undetected. Now, these bodies present a form of danger to cometic wanderers which the large planets do. not occasion. They do not travel in the same general

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level as the large planets, but at considerable inclinations thereto; and thus they range widely above and below that level. The width of the zone is also considerable. fact, the zone does not form a flat ring like the ring of Saturn, but a system shaped like an anchor ring.1 Through this zone, or at least its outskirts, the path of Biela's comet carries it; and it is not altogether impossible that it was while passing through this critical part of its orbit, that it suffered the injuries which have prevented it from returning in recognisable form to the scrutiny of our terrestrial astronomers.

But if it only escaped that danger, it was thenceforward safe until it again returned to the earth's path. It had to pass, indeed, the orbit of giant Jupiter, who is the great disturber of comets, insomuch that a fanciful mind might recognise no inapt description of this planet's qualities in the title cloud-compeller,' given by Homer to Zeus, the Jupiter of the Greek mythology. But there is no danger to Biela's comet in this part of its career, since his course carries him far to the north of Jupiter's orbit. Travelling still farther outwards to the point of its path farthest from the sun, the comet then returns, rounding the zone of small planets at a safe distance, passing far north of the course of Mars, and thence, with con

1 This is the technical name for such rings. Possibly to most of my readers a wedding-ring will seem to present an apter illustration. A wedding-ring would, in fact, be called by a mathematician an 'anchor-ring;' a term not unsuitable, perhaps, in other respects.

tinually increasing rapidity, descending towards the path of the earth as a cloud coming out of the north.'

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Since the comet was last seen it has thrice traversed the enormous orbit here described, passing from a least distance of about eighty millions of miles to its greatest distance amounting nearly to six hundred millions of miles. Whether it has been destroyed as a comet, or whether it has only been so far dissipated as to be invisible in our most powerful telescopes, we do not know. But in either case it has pursued the same general course, for the minutest fragment of its substance would obey as implicitly the law of gravity as the once complete comet, or even as the staider members of the solar family--the planets. Such have been the motions of this singular object, such the vicissitudes to which it has been exposed. There is much that is mysterious in these events, much that, to our feeble conception, appears like a waste of energy. But we must remember that though we are ignorant of the purposes which the comet has fulfilled in its journeyings, and of the effects which have resulted from its dissipation, yet all that has happened to it during its career as a member of the solar family was designed by Him who foresees the end from the beginning.' 'Great and marvellous are Thy works, Lord God Almighty!'

VISITANTS FROM THE STAR DEPTHS.

THERE are some astronomical facts which do not seem at a first view more surprising than others, but which yet, when studied thoughtfully, disclose the most startling thoughts for our consideration. Among these I know none more remarkable than the fact that certain bodies reach our solar system from the stellar depths. The fact is easily stated; and at first we might be disposed to say that it is not particularly surprising. If the spaces round our solar system are tenanted by stars, why should they not be tenanted by comets, or by flights of meteors? and such bodies existing in the star depths, why should they not from time to time be drawn from out those depths by the sun's attractive energy, or be encountered by the solar system as it speeds onwards through space?

But so soon as we begin to enquire into this now undoubted fact, we find ourselves brought face to face with mysteries of the most perplexing nature, and we find that thoughts are suggested which impress upon us most startlingly the wonderful nature of the universe, not in extent only, but in duration, and in the vitality that pervades its every portion.

A comet is seen in the far distant depths of space as a faint and scarcely discernible speck. It draws nearer and nearer with continually increasing velocity, growing continually larger and brighter. Faster and faster it rushes on until it makes its nearest approach to our sun, and then, sweeping around him, it begins its long return voyage into infinite space. As it recedes it grows fainter and fainter, until at length it passes beyond the range of the most powerful telescopes made by man, and is seen no more. It has been seen for the first and last time by the generation of men to whom it has displayed its glories. It has been seen for the first and last time by the race of man itself. Nay more, according to the calculations made by astronomers, the comet has made its first and last visit to the solar system. Of all comets this cannot, indeed, be affirmed; but there are some whose motions will bear no other interpretation.

And now, what meaning are we to attach to a visit such as this? Whether we trace back the comet's past history so far as the imagination or the reason can disclose it to us, or whether we follow its future fate, we are alike appalled by the stupendous time-intervals which are revealed to us.

Whence came the comet? Trace back its path, and we find no place from which it could have started on its course until we consider the stars in the region of the heavens whence the comet appeared to travel. It would be idle to select any star in particular in that region as