“There aren't any stores to sell it right here, anyway. I can give you some energy for now, or make you another engine you can hook up to, and you can get metal for yourself later. There are other ways to collect energy, too, like from waterfalls or waves or wind.”
“Sure, if you're only using it as slow as those sources provide it. Or if you find a really big waterfall, or a dam, of course.”
This time, the thing he gives her isn't a transparent sphere. It's an orange dumbbell.
It's perfectly happy to stay where she puts it in midair.
“No, it's connected to the rest of me. If I made it stronger and you pushed hard then you could use it to push me around.”
“No, you have to have something else to connect it to. If you live in one place a lot you can claim the ground and use that, though.”
He points at the ring of thin glass on the sand around them that followed them down from the rock.
Elsewhere on the beach, the mock-bird-people land.
“So if you've got it right, you should be able to push it around but it won't move by itself, like the one I gave you.”
If she pushes it sideways too much from the glass on the ground then the whole structure can tip over. And when she lets go it starts creeping back to where she put it to start. But she's definitely got the feels-like-it's-stuck-in-goo part.
There's also a faint feeling of something about the glass changing, increasing, as she pushes the glass around. Maybe that's what the “stored energy” he was talking about feels like.
“If you made sure to push back enough so it went down gently rather than bouncing, then you'd have all of the energy that was used to lift the heavy thing up. That's the simplest way to use a waterfall, actually — fill a big bucket at the top and then lower it down.”