almost entirely during the Martian month that
corresponds to our month of August, as never happens with our polar ice.
Hence, though this planet is farther away from the Sun than ourselves,
it does not appear to be colder, or, at any rate, it is certain that the
polar snows are much less thick.

On the other hand, there are hardly ever clouds on Mars; the Martian
atmosphere is almost always limpid, and one can say that fine weather is
the chronic state of the planet. At times, light fogs or a little vapor
will appear in certain regions, but they are soon dissipated, and the
sky clears up again.

[Illustration: FIG. 40.--Diminution of the polar snows of Mars during
the summer.]

Since the invention of the telescope, a considerable number of drawings
have been made, depicting Mars under every aspect, and the agreement
between these numerous observations gives us a sufficient acquaintance
with the planet to admit of our indicating the characteristic features
of its geography, and of drawing out _areographic_ maps (_Ares_, Mars).
Its appearance can be judged of from the two drawings here reproduced,
as made (February, 1901) at the Observatory of Juvisy, and from the
general chart drawn from the total sum of observations (Figs. 41, 42 and
43).

It will be seen at the first glance that the geography of Mars is very
different from that of our own globe: while three-quarters of the Earth
are covered with the liquid element, Mars seems to be more evenly
divided, and must indeed have rather more land than water. We find no
immense oceans surrounding the continents, and separating them like
islands; on the contrary, the seas are reduced to long gulfs compressed
between the shores, like the Mediterranean for example, nor is it even
certain that these gray spots do all represent true seas. It has been
agreed to term _sea_ the parts that are lightly tinged with green, and
to give the name of _continent_ to the spots colored yellow. That is the
hue of the Martian soil, due either to the soil itself, which would
resemble that of the Sahara, or, to take a less arid region, that seen
on the line between Marseilles and Nice, in the vicinity of the
Esterels; or perhaps to some peculiar vegetation. During ascents in a
balloon, the author has often remarked that the hue of the ripe corn,
with the Sun shining on it, is precisely that presented to us by the
continents of Mars in the best hours for observation.

[Illustration: FIG. 41.--