oods, Koku sprang up to obey his master's bidding.

And, as he did so, something happened. The first spark from the fuse,
ignited by the electric current, had reached the slow-burning powder.
There was a crackle of flame, and a dull rumble. Koku sprang up from
the big stone as though shot. What he saw and heard must have alarmed
him, for he gave a mighty jump and started to run, at the same time
shouting:

"Me come, Master!"

"You'd better!" cried the young inventor.

Koku got away only just in time, for when he was half way between the
group of his friends and the big rock, the utmost force of the
explosion was felt. It was not so very loud, but the power of it made
the earth tremble.

The rock seemed to heave itself into the air, and when it settled back
it was seen to be broken up into many pieces. Koku looked back over
his shoulder and gave another tremendous leap, which carried him out of
the way of the flying fragments, some of which rattled on the roof of
the log hut.

"There!" cried Tom. "I guess something happened that time! The rock is
broken up finer than any like it we tried to shatter before. I think
I've got the mixture just right!"

"Bless my handkerchief!" cried Mr. Damon. "Think of what might have
happened to Koku if he had been sitting there."

"Well," said Tom, "he might not have been killed, for he would probably
have been tossed well out of the way at the first slow explosion, but
afterward--well, he might have been pretty well shaken up. He got away
just in time."

The giant looked thoughtfully back toward the place of the experimental
blast.

"Master, him do that?" he asked.

"I did," Tom replied. "But I didn't think you'd walk out of the woods,
just at the wrong time, and sit down on that rock."

"Um," murmured the giant. "Koku--he--he--Oh, by golly!" he yelled. And
then, as if realizing what he had escaped, and being incapable of
expressing it, the giant with a yell ran into the tunnel and stayed
there for some time.

The experiment was pronounced a great success and, now that Tom had
discovered the right kind of explosive to rend the very hard rock, he
proceeded to have it made in sufficiently large quantities to be used
in the tunnel.

"We'll have to hustle," said Job Titus. "We haven't much of our
contract time left, and I have reason to believe the Peruvian
government will not give any extension. It is to their interest to have
us fail, for they will profit by all the w