Europe, Asia and Africa
together form one great island; North and South America another, not
quite so large; then come Australia, Greenland, Madagascar, and so
forth; all the lands being islands, larger or smaller. On the other
hand, except the Caspian Sea and the Sea of Aral, there are no large
seas entirely land-bound. In the case of Mars a very different state
of things prevails, as you will see from the three accompanying
pictures (hitherto unpublished), drawn by the famous English observer,
Dawes (called the Eagle-eyed). The third and best was drawn with
a telescope constructed by your famous optician, Alvan Clark, of
Cambridge, Massachusetts. The dark parts are the seas, the light parts
being land, or in some cases cloud or snow. But in these pictures most
of the lighter portions represent land; for they have been seen often
so shaped, whereas clouds, of course, would change in shape.
The planet Mars, like our earth, turns on its axis, so that it has day
and night as we have. The length of its day is not very different from
that of our own day.
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