"Yup. Fire is a chemical reaction. Fire's approximately what happens when you add this," she pokes oxygen, "to something. If you do it fast. If you do it slow that can be, like... rusting."

"Huh. Okay."

"And this one near fire explodes," she pokes hydrogen, "so it's funny that the two of them make water."

"That is odd."

"Yup. Compounds. Anyway. Things I'm going to need include -"

She produces a shopping list of sorts, naming the substances or things similar when she has words for them.

It's all very interesting.

"I can see if I can find anything around here. I don't think I'll be able to identify it in advance though."

"A lot of it I can't use right away anyway, the end result requires so much precision manufacture that first I have to invent tools that will let me invent tools for it." Sigh. "So don't consider yourself in a terrible hurry or anything."

"All right."

"I'm still going to need money. I can reinvent the first three things, sell them here, but after that I'm going to need more stuff. Obvious options include primitive versions of the thing I need in the long run, like calculators - machines that do math for you. Maybe telegraphs."

"What do telegraphs do?"

"Communicate at a distance. You need to do it in code, at first, it can only do various lengths of "on" and pauses in between."

"So like a messenger hawk, but faster?"

"Much faster. It can take more time to encode the messages than for them to get where they're going."

"Does it take much infrastructure?"

"Yes. Wires, leading from where you're sending to where you're receiving."

"So you'd need to set up before you can do anything with that."

"And it'd be particularly difficult to do across the ocean without my helping in a way I needn't, so that should also help."

"So what are you going to do first?"

"First I need to get all the code written down. It's a desperate long shot that if something happens to me your grandchildren will find a bundle of binary in the attic and decide to run it through optical character recognition and run it, but it's the best backup available and something might happen to me and then I'm stuck somewhere plastinated waiting for those grandchildren or worse. Then... I don't wanna give the Fire Nation any help finding me, so no sewing machines or anything else they'll recognize on a large scale. I'm torn between telegraphs and lightbulbs."

"Lightbulbs?"

"Light without fire."

"Ah."

"Lightbulbs themselves aren't a huge deal but they require generating electricity, which is."

"What's the best way to do that?"

"I'll need magnets, and wires, and something that moves, like a water wheel."