Stacy's intention to give the beast the fright of its life, in which
ambition he succeeded beyond his fondest anticipations.

Getting near enough for his purpose, Stacy slipped from his pony,
hunted about until he found a stick long enough for his purpose, and
with this crept up on the sleeping mule.

With a shrill shriek the lad brought the stick down on the long-eared
animal's rump with a whack that, while it could not have hurt, did all
that he had hoped it might.

Both the mule's hind feet shot up into the air, while the beast with a
short, sharp bray of fright lunged straight ahead.

The guide uttered a shrill exclamation of warning as he saw the mule
tearing through the bushes to the left of the trail. Leaving his two
pack animals, Eagle-eye leaped for the fleeing one.

But he was too late.

All at once the frightened beast appeared to stand on his head, his
hind feet beating a tattoo in the air; then he disappeared altogether.

The Pony Rider Boys, hearing the disturbance, had hurried up, and just
in time to see the final scene in the little tragedy that their
companion had caused.

"What's this? What's this?" demanded the Professor. "What's the
matter?"