For an instant the two white boys stood stock-still, as if turned to stone. Then by a natural impulse, they turned and started to run. But a spear whizzed through the air after them, transfixing itself quivering in a tree just above their heads.

For an instant the two white boys stood stock-still, as if turned to stone.

This brought them to a halt. Weapons they had none, for when they paused they had laid down their rifles and in their precipitate, startled flight had forgotten to pick them up again.

Utterly unnerved by this added sheaf to their bundle of misfortunes, the two Boy Scouts stood facing the Indians who, they had no doubt, formed a hunting or scouting party sent out by the San Blas tribes that made their homes back in the mysterious recesses of the mountains where rose the headwaters of the Chepalta.

CHAPTER XXV.
A CHAPTER OF ACCIDENTS.

In the meantime Rob and Merritt, working waist deep in the muddy shallows, had succeeded, after some rather arduous work, in clearing the stern wheel of its entangling rope. The line had become twisted in and out of the shaft in such a way that it was necessary in places to cut it loose.

When this had been done, Mr. Mainwaring decided that before blowing the whistle to summon back the young hunters they would give the machinery a test. Accordingly, when the canoes had been secured to the shore, Rob reversed the engine and started it up.

For a moment it whirled and chugged away, straining to back the launch off the muddy shallows in which she had grounded. The lightly built craft trembled under the effort. The engine snorted and puffed as more power was applied.

“Hooray! We’re afloat once more!” cried Merritt triumphantly, as the launch was caught in the current and swung free. But at the same instant came an ominous cracking sound. The engine raced wildly and then stopped as Rob shut off the power.