She fetches paper and pencil.

"For the ley, there's - let's say that you lived in a flat world. You could only go side to side or forward or backward, not up or down. You wouldn't be able to see anything above or below you. There's something like that for us, who have up, down, side to side, and forward and backward. It's really hard to move along that, but some things can."

"For the engine..." She sketches a river, and a wheel sticking into it. The wheel is connected to a rod, and then to another wheel. "This is how a watermill works. You can use it to do things like grind grain. It's a very simple engine. There's also steam engines..." And she sketches a fire under the outline of a boiler, with water and rising steam in it. The steam goes into a pipe, then hits a wheel a lot like a windmill. "The fire heats the water, making steam. The steam enters the pipe and goes to push against the fan blades. The center of the fan is usually connected to a stick, which is connected to a special type of wheel called a gear. Do you have anything like these where you're from?"

"There's a water mill down in Haverstead. But no windmills. So... Hot steam makes wind? Or is wind? And then it works like a little windmill?"

"Yes. Steam likes to go upwards and out, and when it can't escape, it pushes against things. If it's in a small pipe, it pushes very fast."

"Huh. Is that because it's steam or because it's hot? Hot air blows out of a house when you open the door in winter."

"It's because it's hot, yes. Heat is a type of energy, and hot gasses that have a lot of energy like to move fast and get bigger."

"Huh. And sounds like you can make big fancy engines out of it. Like the ones downstairs."

"The one downstairs works a bit different - it uses a combination of magic and magnets to turn the rod, since it's safer and the engine can be smaller that way - but the basic idea's the same, yes."

"Engines are faster than using the wind or rowing. We should tell ship people about this when I go home."

"That'd probably help a lot, yeah. Would you like to know more?"

"Yeah!" Lessons are captivating enough that she doesn't want to go explore the ship and play around for at least a couple of hours.

Sarati remembers enough of her early lessons to piece together something age-appropriate, though she occasionally mentions concepts probably past Grenadine's level.

She is a clever, if not brilliant, child. Plenty of it goes over her head but she learns plenty as well.

Sarati occasionally has to get up to check on something in the engines, but is otherwise focused on filling out Grenadine's physics education. 

After a few hours, the view outside the port changes as the star-flecks press closer. The low moaning rises to a howling, and the ship starts to shudder. Sarati stands, says to Grenadine, "There's a storm coming, get yourself buckled in," and puts their papers inside the box forming the table. 

"What's a buckle?"

"A way of securing straps, so you won't fall down if the ship moves too much. Here - " She leads Grenadine over to the side of the ship, and points out the straps. "I'll help you get secured, okay?"

"...Okay." Sarati knows what she's doing.

She settles in next to Grenadine. "This looks like it'll be just a small storm, but I'll need to be steering the ship directly. Do you want me to close the view port?"

"Only if you want."

She looks decidedly uncertain, but... Afraid would not be the right word.

"Okay." She leaves it open, and buckles herself in, then plants her hands on the ship's hull and closes her eyes.

Steering the ship through the storm is tricky; even with one as minor a this the air fills with a sound like static electricity, and the ship keeps pitching forward and back and shaking and shuddering, sometimes rather dramatically. Everything is tied down tightly, though, so while the passengers get jostled the boxes all stay in place.

The view outside brightens, swirls of colored light competing with the rising mist. The frozen lightning grows closer and bigger and some of it starts to move. The ship passes under a few arcs, delicately threading through the tendrils.

Sarati knows what she's doing. Sarati knows what she's doing. It's just like the Witches - don't worry, she's trying to be safe too.

The storm ends after about an hour. Sarati relaxes with a sigh as the view returns to mostly normal. "We're clear. You okay?"

"Yeah. You were right about being strapped in."

"I need to go downstairs and check on the engines. You okay staying up here, or do you want to come with me?"

"The engine is cool, can I watch?"

"Sure."

She heads downstairs, and shows Grenadine the steps of checking the engine for damage or strain. The engine's in good condition, luckily, and doesn't need any maintenance beyond the basics.