But in the day which
follows, of twelve or ten months, the sun has time to melt all, or
nearly all, of the snow of recent formation, reducing it to such a
small area that it seems to us no more than a very white point. And
perhaps this snow is entirely destroyed; but of this there is at present
no satisfactory observation.
Other white spots of a transitory character and of a less regular
arrangement are formed in the southern hemisphere upon the islands near
the pole, and also in the opposite hemisphere whitish regions appear at
times surrounding the north pole and reaching to 50 degrees and 55
degrees of latitude. They are, perhaps, transitory snows, similar to
those which are observed in our latitudes. But also in the torrid zone
of Mars are seen some very small white spots more or less persistent;
among others one was seen by me in three consecutive oppositions
(1877-1882) at the point indicated upon our chart by longitude 268
degrees and latitude 16 degrees north. Perhaps we may be permitted to
imagine in this place the existence of a mountain capable of supporting
extensive ice fields. The existence of such a mountain has also been
suggested by some recent observers upon other grounds.
As has been stated, the polar snows of Mars prove in an incontrovertible
manner that this planet, like the earth, is surrounded by an atmosphere
capable of transporting vapor, from one place to another. These snows
are, in fact, precipitations of vapor, condensed by the cold, and
carried with it successively.
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