"Thirteen words," repeated Tom, as the operator called them back to
him. "I hope that doesn't mean bad luck."

The experiment which Tom Swift had just brought to a successful
conclusion was one of many he had conducted, extending over several
wearying weeks.

As soon as Tom had received the samples of the rock he had begun to
experiment. First he tried some of the explosive that was so successful
in the giant cannon. As he had feared, it was not what was needed. It
cracked the rock, but did not disintegrate it, and that was what was
needed. The hard rock must be broken up into fragments that could be
easily handled. Merely to crack it necessitated further explosions,
which would only serve to split it more and perhaps wedge it fast in
the tunnel.

So Tom tried different mixtures, using various chemicals, but none
seemed to be just right. The trials were not without danger, either.
Once, in mixing some ingredients, there was an explosion that injured
one man, and blew Tom some distance away. Fortunately for him, there
was an open window in the direction in which he was propelled, and he
went through that, escaping with only some cuts and bruises.

Another time there was a hang-fire, and the explosive burned instead of
detonating, so that one of the shops caught, and there was no little
work in subduing the flames.

But Tom would not give up, and finally, after many trials, he hit on
what he felt to be the right mixture. This he took out to the big lot,
and having made a miniature tunnel with some of the sample rock, and
having put some of the explosive in a hole bored in the big chunk Koku
carried, Tom fired the charge. The result we have seen. It was a
success.

A day after receiving Tom's message Mr. Titus came on and a
demonstration was given of the powerful explosive.

"Tom, that's great!" cried the tunnel contractor. "Our troubles are at
an end now."

But, had he known it, new ones were only just beginning.

Tom at once began preparations for making the explosive on a large
scale, as much of it would be needed in the Andes tunnel. Then, having
turned the manufacturing end of it over to his men, Tom began his
preparations for going to Peru.

Mr. Damon was also getting ready, and it was arranged that he, with Tom
and Mr. Titus, should take a vessel from San Francisco, crossing the
continent by train. The supply of explosive would follow them by
special freight.

"We might have gone by Panama except