For a moment Jackson thought Tom had discovered a clew to, or evidences of, some crime.He had an unpleasant suspicion, for an instant, that there was blood on the files, and that it might prove to be the blood of Mr.Nestor.
But the satisfaction that showed on Tom's face did not seem to indicate such dire possibilities as these.
"What is it?" asked Jackson, unable to guess at what Tom was looking through the powerful glass."What do you see?""Metal filings on the grooves of these files," said the young inventor."And, unless I'm greatly mistaken, the particles of filings are from the case of my aircraft silencer!""What!" cried the machinist."Do you mean those are the files used in weakening the outer case of your new machine, so that it burst a little while ago?""That what I think," answered Tom."I know it sounds pretty far- fetched," he went on."But take a look for yourself.If those particles on, the files aren't exactly of the same color and texture as the material of which the silencer case is made, I'll never build another machine."Jackson peered through the powerful glass moving out a little farther from the shack, so as to get the best light possible on the subject of his examination.It was fast getting dark, but there was enough glow in the western sky for his purpose.
"Am I right?" asked Tom.
"You're right!" declared his helper."This is exactly the same metal as that of which your silencer case is made.It's a peculiar mixture of aluminum and vanadium steel.I never knew it used in any shop but yours, and these filings are certainly of that metal.It would seem, Tom, that these were the files used to cut a crease in the case of your silencer to weaken it so it would burst.""My idea exactly!" cried Tom."The spy, who got into my shop insome undiscovered manner, did his work and then fled here to hide.He left his files behind.Mr.Nestor must have been here, either before or after.No, I'll not say that, either.Finding his wallet here doesn't prove that he was here.It might have been brought here by one of the spies and dropped.But I'm sure we're on the track of the men who damaged my airship, as well as those who know something of the mystery of Mr.Nestor.""I agree with you," said Jackson."Of course there's a possibility that the same peculiar metal you used in your silencer case may have been used in some other machine shop, and these files may have come from there, and have been employed in perfectly regular work.But the chances are--""There's only one way to make sure," said Tom."Let's take the files with us and see if they fit in the grooves where the break came.We'll take these back to where we left the Air Scout," and he clinked the files he held.
"We can just about make it before it gets black dark," returned Jackson."But that won't give us any more time to look around here," and he indicated the hut.
"I fancy we've seen all there is to see here," said Tom."Mr.Nestor isn't here, and whether he was or not is a question.Anyhow, some one was here who had something to do with him after his disappearance, I'm positive of that.And I'm sure some one was here who damaged my airship.Now we'll run down both those clews, find out who owns this place, who has been using it, and all we can along that line.So, if you're ready, let's travel."The two set out to make their way back to where they had left the stranded airship.It was fast becoming dark, but they could hurry along with more speed now, as they did not have to stop to look for the marks of the peculiar automobile tires.They had noticed the path along which they had traveled, and in half the time they had spent coming they were back where the Air Scout rested undisturbed in the meadow amid the trees.
Making sure that, as far as they could tell, no one had visited the craft since they had left it, Tom and Jackson compared the file marks on what was left of the broken silencer case with the files they had found in the hut.They used a small, but powerful electric lamp to aid them in thisexamination, as it was too dark to see otherwise, and what they saw caused the young inventor to exclaim:
"That settles it! These were the files used!""That's right!" agreed his assistant."You've called the turn, Tom.The next thing to do is to find who connects with the files.""Yes.To do that and find Mr.Nestor," said Tom."We have plenty of work ahead of us.But let's get nearer civilization and send some word to the folks at home.They'll be getting worried.""It doesn't seem as if there was a way out of here without using an airship," remarked Jackson.
