"Because I was interested. Go on, tell me some more."

"Not now. I want to get this powder in a safe place. I'm a
little nervous about it after that fire. You see if it had
caught, when tightly packed in the boxes, there would have been a
terrific explosion, though it does burn so harmlessly in the open
air. Now let me see--"

Tom was interrupted by the postman's whistle, and a little
later Eradicate came in with the mail that had been left in the
box at the shop door. Tom rapidly looked over the letters.

"Here's the note I want, I think," he said, Selecting one.
"Yes, this is it. 'Permission is hereby granted,' he read, 'to
Thomas Swift to visit,' and so on, and so on. This is the stuff,
Ned!" he cried.

"What is it?"

"A permit to visit the government proving grounds at Sandy
Hook, Ned, and see 'em test that new big gun I was telling you
about. Hurray! We'll go down there, and I'll see how my ideas fit
in with those of the government's experts."

"Did you say 'we' would go down, Tom?"

"I sure did. You'll go with me; won't you?"

"Well, I hadn't thought very much about it, but I guess I will.
When is it?"