Memoirs of the British Astronomical Association. MAP OF MARS.
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Look at the map of Mars, in which the surface appears to be cut up into land and water, continents and oceans. The men who first observed Mars with accuracy saw that some parts were of a reddish colour and others greenish, and arguing from our own world, they called the greenish parts seas and the reddish land. For a long while no one doubted that we actually looked on a world like our own, more especially as there was supposed to be a covering of atmosphere. The so-called land and water are much more cut up and mixed together than ours, it is true. Here and there is a large sea, like that marked 'Mare Australe,' but otherwise the water and the land are strangely intermingled. The red colour of the part they named land puzzled astronomers a good deal, for our land seen at the same distance would not appear so red, and they came at last to the conclusion that vegetation on Mars must be red instead of green! But after a while another disturbing fact turned up to upset their theories, and that was that they saw canals, or what they called canals, on Mars. These were long, straight, dark markings, such as you see on the map. It is true that some people never saw these markings at all, and disbelieved in their existence; but others saw them clearly, and watched them change—first go fainter and then darker again. And quite recently a photograph has been obtained which shows them plainly, so they must have an existence, and cannot be only in the eye of the observer, as the most sceptical people were wont to suggest. But further than this, one astronomer announced that some of these lines appeared to be double, yet when he looked at them again they had grown single. It was like a conjuring trick. Great excitement was aroused by this, for if the canals were altered so greatly it really did look as if there were intelligent beings on Mars capable of working at them. In any case, if these are really canals, to make them would be a stupendous feat, and if they are artificial—that is, made by beings and not natural—they show a very high power of engineering. Imagine anyone on earth making a canal many miles wide and two thousand miles long! It is inconceivable, but that is the feat attributed to the Martians. The supposed doubling of the canals, as I say, caused a great deal of talk, and very few people could see that they were double at all. Even now the fact is doubted, yet there seems every reason to believe it is true. They do not all appear to be double, and those that do are always the same ones, while others undoubtedly remain single all the time. But the canals do not exhaust the wonders of Mars. At each pole there is an ice-cap resembling those found at our own poles, and this tells us pretty plainly something about the climate of Mars, and that there is water there.

This ice-cap melts when the pole which it surrounds is directed toward the sun, and sometimes in a hot summer it dwindles down almost to nothing, in a way that the ice-caps at the poles of the earth never do. A curious appearance has been noticed when it is melting: a dark shadow seems to grow underneath the edge of it and extends gradually, and as it extends the canals near it appear much darker and clearer than they did before, and then the canals further south undergo the same change. This looks as if the melting of the snow filled up the canals with water, and was a means of watering the planet by a system totally different from anything we know here, where our poles are surrounded by oceans, and the ice-caps do not in the least affect our water-supply. But, then, another strange fact had to be taken into consideration. These straight lines called canals ran out over the seas occasionally, and it was impossible to believe that if they were canals they could do that. Other things began to be discussed, such as the fact that the green parts of Mars did not always remain green. In what is the springtime of Mars they are so, but afterwards they become yellow, and still later in the season parts near the pole turn brown. Thus the idea that the greenish parts are seas had to be quite given up, though it appeared so attractive. The idea now generally believed is that the greenish parts are vegetation—trees and bushes and so on, and that the red parts are deserts of reddish sand, which require irrigation—that is to say, watering—before anything can be grown on them. The apparent doubling of the canals may be due to the green vegetation springing up along the banks. This might form two broad lines, while the canal itself would not be seen, and when the vegetation dies down, we should see only the trench of the canal, which would possibly appear faint and single. Therefore the arrangements on Mars appear to be a rich and a barren season on each hemisphere, the growth being caused by the melting of the polar ice-cap, which sends floods down even beyond the Equator. If we could imagine the same thing on earth we should have to think of pieces of land lying drear and dry and dead in winter between straight canal-like ditches of vast size. A little water might remain in these ditches possibly, but not enough to water the surrounding land. Then, as summer progressed, we should hear, 'The floods are coming,' and each deep, huge canal would be filled up with a tide of water, penetrating further and further. The water drawn up into the air would fall in dew or rain. Vegetation would spring up, especially near the canal banks, and instead of dreary wastes rich growths would cover the land, gradually dying down again in the winter. So far Mars seems in some important respects very different from the earth. He is also less favourably placed than we are, for being so much further from the sun, he receives very much less heat and light. His years are 687 of our days, or one year and ten and a half months, and his atmosphere is not so dense as ours. With this greater distance from the sun and less air we might suppose the temperature would be very cold indeed, and that the surface would be frost-bound, not only at the poles, but far down towards the Equator. Instead of this being so, as we have seen, the polar caps melt more than those on the earth. We can only surmise there must be some compensation we do not know of that softens down the rigour of the seasons, and makes them milder than we should suppose possible.

Of course, the one absorbing question is, Are there people on Mars? To this it is at present impossible to reply. We can only say the planet seems in every way fitted to support life, even if it is a little different from our earth. It is most certainly a living world, not a dead one like the moon, and as our knowledge increases we may some day be able to answer the question which so thrills us.

Our opportunities for the observation of Mars vary very greatly, for as the earth's orbit lies inside that of Mars, we can best see him when we are between him and the sun. Of course, it must be remembered that the earth and the other planets are so infinitely small in regard to the space between them that there is no possibility of any one of them getting in such a position that it would throw a shadow on any other or eclipse it. The planets are like specks in space, and could not interfere with one another in this way. When Mars, therefore, is in a line with us and the sun we can see him best, but some of these times are better than others, for this reason—the earth's orbit is nearly a circle, and that of Mars more of an ellipse.

ORBITS OF THE EARTH AND MARS.

Look at the illustration and remember that Mars' year is not quite two of ours—that is to say, every time we swing round our orbit we catch him up in a different place, for he will have progressed less than half his orbit while we go right round ours.

Sometimes when we overtake him he may be at that part which is furthest away from us, or he may be at that part which is nearest to us, and if he is in the latter position we can see him best. Now at these, the most favourable times of all, he is still more than thirty-five millions of miles away—that is to say, one hundred and forty times as far as the moon, yet comparatively we can see him very well. He is coming nearer and nearer to us, and very soon will be nearer than he has been since 1892, or fifteen years ago. Then many telescopes will be directed on him, and much may be learned about him.

For a long time it was supposed that Mars had no moons, and when Dean Swift wrote 'Gulliver's Travels' he wanted to make the Laputans do something very clever, so he described their discovery of two moons attending Mars, and to make it quite absurd he said that when they observed these moons they found that one of them went round the planet in about ten hours. Now, as Mars takes more than twenty-four hours to rotate, this was considered ridiculous, for no moon known then took less time to go round its primary world than the primary world took to turn on its own axis. Our own moon, of course, takes thirty times as long—that is a month contains thirty days. Then one hundred and fifty years later this jest of Dean Swift's came true, for two moons were really discovered revolving round Mars, and one of them does actually take less time to complete its orbit than the planet does to rotate—namely, a little more than seven hours! So the absurdity in 'Gulliver's Travels' was a kind of prophecy!