"Continual sunlight! He can't be inhabited, then?" The architect knew
very little about the planets. He had been included in the party
because, along with his professional knowledge, he possessed remarkable
ability as an amateur antiquarian. He knew as much about the doings of
the ancients as the average man knows of baseball.

Dr. Kinney shook his head. "Not at present, certainly."

Instantly Jackson was alert. "Then perhaps there were people there at
one time!"

"Why not?" the doctor put it lightly. "There's little or no atmosphere
there now, of course, but that's not saying there never has been. Even
if he is such a little planet--less than three thousand, smaller than
the moon--he must have had plenty of air and water at one time, the same
as the Earth."

"What's become of the air?" Van Emmon wanted to know. Kinney eyed him in
reproach. He said:

"You ought to know. Mercury has only two-fifths as much gravitation as
the earth; a man weighing a hundred and fifty back home would be only a
sixty-pounder there. And you can't expect stuff as light as air to stay
forever on a planet with no more pull than that, when the sun is on the
job only thirty-six millions miles away."

"About a third as far as from the Earth to the sun," commented the
engineer. "By George, it must be hot!"