ore I can get it home.

"As for either of us staying here on guard, I don't quite see the need
of that. This looks like the jumping-off place to me. I don't believe
there's a native within miles. I didn't see any houses as we came down,
and I think Silent Sam will be perfectly safe here. No one can run off
with him, anyhow. He'd be as hard to start as an automobile with all
four wheels gone. Let's leave it here and both walk back."

"All right," agreed Jackson. "That suits me. Might as well leave our
togs here, too. It will be easier walking without them," and he began
taking off the fur-lined suit, his cap, and his goggles, such as he and
Tom wore against the piercing cold of the upper regions.

"We can stuff them in the cockpit and leave them," went on the
mechanician, as he divested himself of his garments. As he stowed them
away in his seat he gave one more look at the broken muffler. As Tom
Swift said, his new silencer had literally blown up, a large piece
having been torn from the gas chamber.

Something that Jackson saw caused him to utter an exclamation that
brought Tom Swift to his side.

"What is it?" asked the young inventor.

"Look!" was the answer. "See! Just at the edge of that break! It's
been filed to make the metal thinner there than anywhere else. You
didn't do that, did you?"

"I should say not!" cried Tom. "Why, to file there would mean to weaken
the whole structure."

"And that's exactly what's happened!" declared Jackson, as he gave
another look. "Some one has filed this nearly through--leaving only a
thin metal skin, and when the gas pressure became too much it blew out.
That's what happened!"

Tom Swift made a quick but thorough examination.

"You're right, Jackson!" he exclaimed. "That was filed deliberately to
cause the accident. And it must have been done lately, for I carefully
inspected the silencer when I put it on, and it was in perfect order.
There's been spy work here. Some one got into the hangar and filed that
casing. Then the accumulated pressure of the gases did the rest."

"As sure as you're alive!" agreed Jackson. "Maybe that's what Gale did
when he called."

"No," returned Tom, shaking his head, "he didn't get a chance to do
anything like that. I watched him all the while. But perhaps this is
what he referred to when he said he and his company would repudiate any
act of that spy with the gold tooth--Lydane, so Gale said his name was.
Maybe that's what Lydane did."