pressed eastward, the antelopes began circling, and their course
brought them in time much nearer to Rhoda. It was an old
trick--making the frightened but fleet animals run in a
half-circle. Rhoda was cutting across to get within rifle shot.

The breeze soon carried the scent of the pursuing party to the
nostrils of the antelopes, too; but they did not notice Rhoda. She
brought up her rifle, shook her pony's reins, and in half a minute
stood up in her short stirrups and drew bead on the white spot
behind the fore shoulder of one of the running antelopes.

The distance was almost the limit for that caliber of rifle; but
the antelope turned a somersault and lay still, while its mates
turned off at a tangent and tore away across the plain.

It was several minutes before Walter and the other girls rode up.
Rhoda had not dismounted. She was not looking at the dead antelope.
Instead, she had unslung her glasses again and was staring through
them westward--toward the slate-colored cloud that was climbing
steadily toward the zenith.

When the ponies were halted and the sound of their hoofs was
stilled, the young people could hear a moaning noise that seemed to
be approaching from the direction toward which they were facing at
that moment--the west.

"Oh!" cried Nan, "what is that?"

"Have you seen it before?" demanded Rhoda, shutting the glasses and
putting them in the case.