they would themselves be imprisoned by the wall. So
they had to leave some place to get around the wall,
and, if the wall was visible, all strangers or enemies
would find the place to go around it and then the wall
would be useless. So the Flatheads cunningly made their
wall invisible, believing that everyone who saw the
entrance to the mountain would walk straight toward it,
as we did, and find it impossible to go any farther. I
suppose the wall is really high and thick, and can't be
broken through, so those who find it in their way are
obliged to go away again."

"Well," said Dorothy, "if there's a way around the
wall, where is it?"

"We must find it," returned Ozma, and began feeling
her way along the wall. Dorothy followed and began to
get discouraged when Ozma had walked nearly a quarter
of a mile away from the entrance. But now the invisible
wall curved in toward the side of the mountain and
suddenly ended, leaving just space enough between the
wall and the mountain for an ordinary person to pass
through.

The girls went in, single file, and Ozma explained
that they were now behind the barrier and could go
back to the entrance. They met no further obstructions.

"Most people, Ozma, wouldn't have figured this thing
out the way you did," remarked Dorothy. "If I'd been