It is found that his surface is divided into land and water, like the surface of our own earth.  But his seas and oceans are not nearly so large compared with his continents and lands.  You know that on our own earth the water covers so much larger a surface than the land that the great continents are in reality islands.  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case of Mars a very different state of things prevails, as you will see from the three accompanying pictures (hitherto unpublished), drawn by the famous English observer, Dawes (called the Eagle-eyed).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.  Our earth turns once on its axis in ——­ but before reading on, try to complete this sentence for yourself.  Every one knows that the earth’s turning on its axis produces day and night, and nine persons out of ten, if asked how long the earth takes in turning round her axis, will answer, 24 hours; and if asked how many times she turns on her axis in a year, will say 365 times, or if disposed to be very exact, “about 365-1/4 times.”  But neither answer is correct.  The earth turns on her axis about 366-1/4 times in each year, and each turning occupies 23 hours 56 minutes and 4 seconds and 1 tenth of a second.  We, taking the ordinary day as the time of a turning or rotation, lose count of one rotation each year.  It is necessary to mention this, in order that when I tell you how long the day of Mars is, you may be able correctly to compare it with our own day.  Mars, then, turns on his axis in 24 hours 37 minutes 22 seconds and 7 tenth-parts of a second.  So that Mars requires 41 minutes 18 seconds and 6-tenths of a second longer to turn his small body once round than our earth requires to turn round her much larger body.  The common day of Mars is, however, only about 39 minutes longer than our common day.

Mars has a long year, taking no less than 687 of our days to complete his circuit round the sun, so that his year lasts only about one month and a half less than two of ours.

[Illustration:  APPEARANCE OF MARS, 1852, MARCH 23, 5 H. 45 M., Greenwich Mean Time.  Power of Telescope, 358; 6-1/3 inch object-glass]

[Illustration:  APPEARANCE OF MARS, 1852, FEBRUARY 3, 6 H. 50 M., Greenwich Mean Time.  Power of Telescope, 242 and 358 on 6-1/3 inch object-glass.]