"I suppose." Sigh. "Well, I'm staying right here. I don't like governments much, as a rule. But I'll take their money."

"I'll go talk to them."

He leaves, at least for the time being. The next person to come in is a young woman who looks around at everything suspiciously.

He's in the workshop, but pings his voice over the PA. "I'll be out front in a moment!" And heads out about a minute later. "Want help finding anything?"

"I'd like to know how you travel and whether you ever take people with you."

"Sorry, flat no. I could maybe cook up a vehicle if you're running from something, though."

"I never run. Do you have evidence that any of your wares will still exist in the morning if I buy them?"

"Only my word. Though I suppose a knowledge of how the things I'm selling actually work, so I could explain some underlying principles, if you and I both have the patience to get through an interrogation about that."

"That sounds excellent. Are they the sorts of things that are obvious once you hear them?"

"Some of them. Controlled-lightning would take a lot of background, for example. Are you familiar with smelting metals at all? Or perhaps you should pick the topic, if you're wanting assurance."

"I am... somewhat familiar with some aspects of metalworking."

"So, bronze is a combination of two metals. Copper and a bit of tin. Copper and tin, as it happens, are pure metals. You can separate bronze into copper and tin, but you can't separate those two into anything else. Copper and tin, they're not combinations of anything else, they're a stable way that matter can be. We call those stable substances 'elements'. Iron is as well, but the best iron is not pure iron. It's carefully combined with small amounts of carbon, and possibly other metals, to form 'steel'- An alloy of iron, much like bronze is an alloy of copper. Most things are complex combinations of other elements. What would you say the smallest possible amount of, oh, water, one could have is? If you had some way to see details much smaller than even one of your hairs, would you predict that you could keep dividing a droplet of water forever? Where would it stop, if it does?"

She suspects that he's asking so that he can gauge which claims she'll be able to verify. But she's not sure what else she can do but go along with it at least a little. At least if she doesn't want to try his patience with accusations.

"That sounds like a philosophical question about the definition of water, at least as much as it's an engineering question."

"It's an engineering question about the definition of water. Atoms. The fundamental building block of the universe. So small you can't see individual ones, but everything is atoms in the end of ends. Each element is a kind of atom. Water is one oxygen paired with two hydrogen. They're incredibly tiny- But they're all the same as each other, barring some subtleties. How to demonstrate this, hmm..."

"If it's an important part of the background knowledge needed to create your devices I imagine it has all sorts of impacts on the world, but I suppose you'd need to find something I could be sure didn't have another explanation."

"Here's one that ought to be supporting if not definitive. If you burn something, it turns to ash, yes? The ash weighs less than the burned thing. But if you burn something inside an air-tight container, it will weigh precisely as much as it did before. Of course, if you burn something inside an air-tight container it won't burn very long without the oxygen in the air being turned to ash and unbreathable gas, putting the fire out, as fire is a process of conversion. There's lots of other possible explanations now that I think about it actually... I don't exactly do this often, you might be able to tell."

"It can't be a very normal sort of job, it's not quite teaching... Anyway, are you implying ash is made of different kinds of atoms?"

"Yes. Many of them the same that were in the wood or whatever, and some that were in the air. Oh, air has weight and is made of elements just the same - they're simply light enough to fly freely rather than being pulled to the ground. If it got cold enough the air would turn liquid, then solid. Oh, there's an idea, want to see some frozen and liquid air? Components of air, at least."

"Yes. I would love that."

"Be right back!"

He comes out with a silver cylinder of liquid nitrogen, and a stryofoam box of dry ice, and a couple little beakers half full of water.

He carefully pours liquid nitrogen from the insulated container into the beaker. The surface boils vigorously and mist pours off it, frost forming on the outside. It feels very cold, though.

She moves as if she's going to reach for it, and then stops. On the one hand, she could get hurt. On the other hand, she could believe an ice burn.

"'M not responsible for any injuries. You can lose fingers if you immerse them in this stuff. Touching the outside would be safer."

"Of course."

That's terrible but not necessarily as bad as the upside here is good. She pokes the outside gently with the tip of her left pinky and pulls back immediately.

The beaker is nudged slightly and continues to boil. The boiling has started to settle down some now.

It's very cold. Freezing, even. Just touching it for a bare moment doesn't do lasting harm probably.

"I confess I can't tell by looking at it that this is a component of air."

"I could get some lox out, you can breathe that. You can breathe this too, but it doesn't have the stuff that powers burning - and our own bodies. Oh, the air coming off it will put out a flame, though!"