and these, again, revolved more rapidly than the outermost portions.

In fact, each part of each Ring went at the same pace which would have been taken by any ordinary satellite, revolving at just that distance from the planet. This once and for all settled the question as to their being each one a solid and complete whole.

It is thought not at all unlikely that, once upon a time, other planets-if not all of them were loose masses or clouds of tiny particles whirling in company around the Sun, and that gradually, as centuries and millenniums passed, these particles drew closer together, forming masses, and in time taking shape as worlds. It may have been thus. If so, Saturn's rings will perhaps in time draw together in a like manner, the nearer parts joining the body of the planet, while more distant parts might possibly coalesce into moons."

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Saturn, therefore, at his present stage may be actually a younger member of the family than Jupiter, not so far developed.

Yet the thought brings perplexity; for no signs have been seen of the violent hurricanes and perpetual tornadoes which seem to rage on Jupiter, caused, no doubt, by the great heat of that planet. Saturn appears to be in a more quiet condition than his tempestuous twin; hot enough to keep his oceans aloft in the form of dense clouds, though perhaps this is only conjecture—perhaps no longer a scene of furious storms and whirlwinds. But why it should be so is a mystery, seeing that Saturn is the lighter in make, which would seem to imply a less cooled condition.

In any case, and even if he really is cooler and less

turbulent than his comrade in the skies, Saturn can hardly be looked upon as ready to support any kind of animal-life known to us, so long as his waters still float in his atmosphere as steam or vapour.

or less

Uranus and Neptune are probably more going through the same stages of development as the great twins.

“Not from the stars do I my judgment pluck;
And yet methinks I have astronomy,

But not to tell of good or evil luck,

Of plagues, of dearths, of season's quality;
Nor can I fortune to brief minutes tell,

Pointing to each his thunder, rain and wind,
Or say with princes if it shall go well,
By oft predict that I in heaven find."

SHAKESPEARE.

H

PART VIII

OUR SOLAR SYSTEM

I. MUTUAL INFLUENCES

THE System, of which our Sun is head and ruler, vast in comparison with our Earth yet small in comparison with the Universe, must not be pictured as a piece of fixed and rigid mechanism. On the contrary, both as a whole and in all its parts, it is in perpetual motion. From the centre to the outskirts, it is never for one instant at rest.

To make this clear, recall the various movements of Earth and Moon.

First the Earth spins incessantly, day and night. Second: the Moon spins on her own axis, and travels round the Earth once every month. Third both Earth and Moon journey round the Sun in close company once in the course of twelve months. And fourth : both Earth and Moon wander through space on a vast and mysterious voyage, travelling with the Sun and all the other planets and satellites.

Viewed in the first and second of these aspects, we can talk of the Moon as our Moon. But viewed in the third and fourth, she is a planet, just as our Earth is a planet.

As truly as Earth is under the Sun's dominion, so also

is the Moon. Both are so heavily pulled by the Sun that both would rush towards him, and would drop down on his fiery surface, were it not for the vehement impetus and the strong outward pull of their own swing around him. This outward drag of rapid motion just serves to balance the inward drag of his attraction.

In addition, the Earth has a powerful influence over the Moon, so powerful as to keep her small friend always near. But when we speak of the Moon as going round the Earth, while the Earth goes round the Sun, we do not state the matter fairly. Earth and Moon travel in company, each controlled by the Sun, and each more or less affected by the other.

The Earth's journey is far from being a smooth and even line, since she is constantly swayed, not only in a tiny fashion by the weak attraction of the Moon, but also by the pull of any passing planet. And the Moon is far more irregular in her advance, because, from her light weight, she is so much more easily drawn this way and that way.

So her orbit really is a complicated affair, since it is at one and the same time a pathway round the Earth, a pathway round the Sun, a pathway through space, and a pathway perpetually affected by the influence of her neighbours. This last is true also of all planets.

As she swings to and fro in a series of bends or scallops round and with the Earth-not in loops, but in curvesshe is now on one side of us, now on the other, now between us and the Sun, now on the farther side away from the Sun, continually changing her speed to fit in with the forward or the backward pull of the Earth. But all the time she is compelled to press steadily

forward on her true main pathway round the Sun, if she would not be dragged down upon his blazing surface.

And as Earth with her Moon journeys round the Sun, so Mars with his two tiny moons, and Jupiter with his ten, and Saturn with his ten, and Uranus with his one, and Neptune with his four, travel in their orbits. All these other moons are influenced by their "primaries and by their companion-moons, hurried on or drawn back, from time to time, on their various orbits. So each member of the family has power to help or to hinder other members.

A fresh thought comes in here. As above said, our Earth has two distinct forward movements: first, round the Sun once each year; secondly, onward with the Sun through Space. And this means that she never once in all the ages, so far as we can tell, comes back to any earlier position in the heavens. Though she does travel round and round the Sun, and though we talk of the "plane" or level of her pathway, it is not strictly a "plane" at all.

For the Sun himself is travelling onward and upward -if we may speak of "upward" where no "up" or "down" exists, except as arbitrarily named by us on our little Earth. Still, from our point of view, north of the equator, his peregrination with his family of planets is upward.

Therefore also the journeying of our Earth really is, not a perpetual circling round and round on one level, but a corkscrew-like advance in a ceaseless spiral. And this, which is true of our Earth, is true of all the planets of our Solar System, and probably of all other planets