"
This happened a little later, and soon they could observe the
great ball of fire hanging in space.
"It seems to be smaller than when we were on the earth, doesn't it?"
asked Mark.
"It is seemingly smaller," replied Professor Henderson. "We are
going away from the sun you know. Mars is not as close to it as
we are on our planet--I mean the one we have just left--is
ninety-two millions of miles from the sun, while Mars is one
hundred and forty-one millions of miles away, though its orbit is
so eccentric that distance varies about thirteen millions of
miles. That is, it may be thirteen millions of miles more than
its mean, or average, distance, so that at times it is as far
away from the sun as one hundred and fifty-four millions of
miles."
"My! That's a good ways," observed Mark.
"Yes," went on Mr. Henderson, "and, in consequence, the light and
heat received by Mars from the sun is a little less than half of
that which our earth receives."
"Whew! We'll be mighty cold in winter--if we arrive in winter,"
said Jack with a shiver.
"Unless the Martians have a means of making up for this loss of
light and heat," said Mr.
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