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.

[Illustration: 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
t