Looking at him thus, through even the most powerful telescopes and under the best conditions, does not mean what people at one time seemed to think that it ought. It does not mean seeing human beings, or trees, or villages, or towns. But it does mean seeing more than can be seen on any other planet in our System, or in the whole Universe.

It means seeing hazy outlines, which probably may be lands, continents, ocean-beds; and ice-caps hundreds of miles in diameter; and clouds or masses of cloud; and mysterious straight lines, also hundreds of miles in length; and faint signs here and there of possible vegetation.

With Venus, so far as we can tell, we seldom if ever catch a glimpse of the actual body of the planet, but only look on her dazzling vesture of clouds. With Mars things are widely different. Not only do we constantly look on his solid surface, but we can study its changes, note its varieties of seasons, measure the extent of its snow-caps in different months, and of its probablelakes and streams, and even speculate on the growth of its possible—vegetation.

For the surface of this celestial friend of ours shows a variety of markings of one kind and another; some of which observers are more and more sure must mean certain realities.

That astronomers are not fully agreed on such subjects need not worry or discourage anybody. Like all human beings, observers of heavenly bodies are liable to make mistakes, and even to be for a time quite convinced of explanations which later are proved to be wrong. Half the scientific knowledge which we now

possess is built upon the ruins of past errors; and many of the theories which are widely accepted at this moment may have in time to give place to other and more remarkable realities.

And even when the theories or explanations offered are not right, and must in time be displaced by others, still it has been better to know all along that some sort of understanding of the puzzle was within our reach, than to have been utterly and hopelessly nonplussed.

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This was once pointed out to me by a wise and able clergyman-friend, with regard to certain deeper mysteries on questions yet more profound. What I say may not be the right explanation," he said. "But it is good to know that some explanation is possible, though the real one may be different and far more wonderful.”

His words, true of the mightier mysteries of Life and Death, are true also about these lesser perplexities. It is worth while to conjecture a way out-worth while to find some sort of possible clue-even though our conjectures may some day prove to be mistaken.

Only, it is also well to avoid over-positiveness, and to be willing to find ourselves in the wrong. Which means willingness to accept readily fresh light thrown upon difficult questions, when it comes.

II. Two LITTLE MOONS

Mars, in place of being nearly eight thousand miles through like Earth and Venus, is only about four thousand three hundred miles; and his weight is about

one-ninth that of Earth. This means a greatly lessened power of attraction for things on his surface.

It means, too, that objects on that world weigh much less than they would weigh on Earth; the downward drag being so much slighter. A strong man here can at most leap only a few feet into the air. But on Mars the effort which here carries him up three or four feet might there lift him easily over a good-sized house if houses are built on Mars. All our systems of weights and measures would have to be altered for use under such conditions.

Still, thus far that little world has been able to keep possession of an atmosphere, or at all events of a good deal of it; instead of losing practically the whole, like the Moon.

Two tiny moons travel with the Red World in his annual journey round the Sun, on an orbit about half as far off again as the orbit of Earth. Their names are Phobos and Deimos, and the bigger of the two is a mere large ball, some twenty miles in diameter. Which is to say that it could be placed between two of our towns, lying twenty-five miles apart, without touching either. Not, however, without overshadowing either, for it would tower twenty miles high in the air.

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Phobos journeys at a fine rate round Mars-his primary as a planet is always called with reference to any of his moons-getting round once in about seven hours and a half, instead of taking four weeks for the tour, as our Moon does. So, if Mars, or Mars' inhabitants, should reckon the months by the biggest and nearest moon, the result would be: three Martian months in one Martian day! A very curious arrange

ment according to our earthly notions. The "day" of Mars, due to his spin on his axis, lasts slightly longer than our earthly day.

But the year of Mars is not far short of two earthly years. Not only is his pathway longer than ours, just as ours is longer than the orbit of Venus, but also his pace is slower than ours, precisely as ours is slower than that of Venus, and for the same reason. Because the distance is greater, the drawing power of the Sun is less; and because that drawing power is less, Mars does not need to travel so fast as Earth to avoid being dragged down upon the Sun. Each planet's speed has to be exactly enough to counterbalance the Sun's pull.

A remarkable sight on the planet is its apparent snow-caps, real white caps, at the north and south poles.

In studying other worlds of our Solar System, we naturally give them earthly names; and not only to the worlds as a whole, but to parts of those worlds. We speak of the north pole, the south pole, the equator, and so on, of each; and the position of poles and equator is settled by the slant of the planet's axis. Sometimes that slant is greater, sometimes it is less than the slant of Earth's axis. This slant is always with reference to the Plane of the Ecliptic.

Of course you know already that the Ecliptic is the seeming path of the Sun through the year, among certain constellations; the line along which he appears to travel, in consequence of our own annual journey round him, which causes us to see him against one group of stars after another.

And the Plane of the Ecliptic is the flat surface—

if such a term may be used where there is no surface— which lies within the whole circle of that Ecliptic. You may draw a circle on a piece of paper, and the plane of that circle is the part of the paper which it encloses, only the paper must lie flat, or it would not be a plane. Or, again, you may imagine a circle in the air, formed by a slender wreath of smoke, and the plane of that circle would be the round space enclosed by the smoke; only, once more, it must be level in shape, or it could not be called a plane.

All the planets of our System keep very nearly—not quite, but nearly to the plane or the level of the Ecliptic; and all, or nearly all the planets' axes slant a little to that plane. They do not stand bolt upright to it, but lie slightly over.

It is this slant of the axis of our Earth which gives us the various seasons; and if our axis were bolt upright, we should have the same weather all the year round, over all the Earth. With other planets, their weather is greatly affected by the degree in which the axis of each stands more upright or leans more over towards the plane of the Ecliptic.

Mars, like the rest, has a slant. This means that his two poles-like our two poles-take turns in the course of the planet's year to be turned towards the Sun and away from the Sun. And this means, as with us, the summers and winters of the northern and southern hemispheres. So Mars, like Earth, has summers and winters and intervening half-seasons.

In one part of his long year, when the northern hemisphere is towards the Sun, the northern half has summer and the southern half has winter. Then,

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