something that filled them with terror.

Between the two trees, and seemingly bound to them by a great coiled
rope, spotted and banded, was the body of Professor Bumper. His arms
were pinioned to his sides and there was horror and terror on his face,
that looked imploringly at the youths from above the topmost coil of
those encircling him.

"What is it?" cried Mr. Damon, as he ran pantingly up. "What has
caught him? Is it the giant iguana?"

"It's a snake--a great boa!" gasped Tom. "It has him in its coils.
But it is wound around the trees, too. That alone prevents it from
crushing the professor to death.

"Ned, be ready with your rifle. Put in the heaviest charge, and watch
your chance to fire!"

The great, ugly head of the boa reared itself up from the coils which
it had, with the quickness of thought, thrown about the man between the
two trees. This species of snake is not poisonous, and kills its prey
by crushing it to death, making it into a pulpy mass, with scarcely a
bone left unbroken, after which it swallows its meal. The crushing
power of one of these boas, some of which reach a length of thirty
feet, with a body as large around as that of a full-grown man, is
enormous.

"I'm going to fire!" suddenly cried Tom. He had seen his chance and he
took it. There was the faint report--the crack of the electric
rifle--and the folds of the serpent seemed to relax.

"I see a good chance now," added Ned, who had taken the small charge
from his weapon, replacing it with a heavier one.

His rifle was also discharged in the direction of the snake, and Tom
saw that the hit was a good one, right through the ugly head of the
reptile.

"One other will be enough to make him loosen his coils!" cried Tom, as
he fired again, and such was the killing power of the electric bullets
that the snake, though an immense one, and one that short of
decapitation could have received many injuries without losing power,
seemed to shrivel up.

Its folds relaxed, and the coils of the great body fell in a heap at
the roots of the two trees, between which the scientist had been
standing.

Professor Bumper seemed to fall backward as the grip of the serpent
relaxed, but Tom, dropping his rifle, and calling to Ned to keep an eye
on the snake, leaped forward and caught his friend.

"Are you hurt?" asked Tom, carrying the limp form over to a grassy
place. There was no answer, the savant's eyes were closed and he
breathed but f