The opponents of the doctrine of the Plurality of Worlds allow that a
greater probability exists of Mars being inhabited than in the case of
any other planet. His diameter is 4100 miles; and his surface exhibits
spots of different hues,--the _seas_, according to Sir John Herschel,
being _green_, and the land _red_. “The variety in the spots,” says
this astronomer, “may arise from the planet not being destitute of
atmosphere and cloud; and what adds greatly to the probability of this,
is the appearance of brilliant white spots at its poles, which have
been conjectured, with some probability, to be snow, as they disappear
when they have been long exposed to the sun, and are greatest when
emerging from the long night of their polar winter, the snow-line then
extending to about six degrees from the pole.” “The length of the day,”
says Sir David Brewster, “is almost exactly twenty-four hours,--the
same as that of the earth. Continents and oceans and green savannahs
have been observed upon Mars, and the snow of his polar regions has
been seen to disappear with the heat of summer.” We actually see the
clouds floating in the atmosphere of Mars, and there is the appearance
of land and water on his disc. In a sketch of this planet, as seen in
the pure atmosphere of Calcutta by Mr. Grant, it appears, to use his
words, “actually as a little world,” and as the earth would appear at
a distance, with its seas and continents of different shades. As the
diameter of Mars is only about one half that of our earth, the weight
of bodies will be about one half what it would be if they were placed
upon our globe.