As a physical world Mars bears a most striking resemblance to our Earth.
The length of its year is six hundred and eighty-seven of our days, and
the length of its day is twenty-four hours and thirty-seven minutes. Its
diameter is about one-half that of the Earth and its distance from the
Sun is 142,000,000 miles. Even from our own world we can discern
through a good telescope the changing colors of the planet, due to the
recurring seasons, each one of which is almost twice the length of ours.

There is relatively much less water on Mars than is found on our Earth,
and gravity on its surface is only thirty-eight per cent. of terrestrial
gravity. Imagine, then, how light everything must be. This may account
somewhat for the physical proportions of its inhabitants, for they are
over twice our size, and in appearance resemble us but little. They have
four arms, two extra ones extending from a point just above the knees.
The two lower arms act as servants to the two higher. Thus are the four
used at one time in harmony.

Mars is an older world than ours, and although it receives only one-half
as much heat from the sun yet it is almost of the same temperature,
owing to a peculiar condition of the atmosphere which we would call
"heat retentivity."

Some scientists and philosophers will at once say that such atmospheric
conditions are contrary to reason and natural law, but they must be
informed that on Mars there are chemical elements and affinities not
known in our world. It requires but little change in the elementary
construction of the atmosphere to render it capable of strong
heat-retaining properties.

Standing on the surface of this planet, my attention was easily