This chapter is filled with talky talk talk talk. Nemo explains that he has all of the instruments he needs to judge the progress of his vessel on the wall in his room. But in order to truly understand how it all goes down, well… the chapter title kind of gives it away.
Electricity is the key to the Nautlius's awesomeness. And not just any kind of electricity, but a wacky, special kind of electricity.
At this point, Aronnax and Nemo have a conversation that's pretty tedious and, scientifically speaking, not quite correct. What it boils down to is that Nemo gets his electricity from sodium, which is manufactured by coal from his underwater coalmines. Yeah, don't waste too much time wrapping your head around it. Just know that Nemo has found a way to use electricity to do pretty much everything: drive his submarine, power the lights on board, etc.
Now Nemo continues the tour. Aronnax tells us that he's already familiar with the forward part of the vessel, which is 115 feet long. Now it's time for the back.
When they reach the center of the ship, Nemo tells Aronnax that they have a special dinghy (a small boat, sort of like a lifeboat) on board, one that can be stowed safely on the side of the sub even when it's underwater. It's also attached to the Nautilus by a special cord so that Nemo can call his sub back to him when he's done dinghy-ing about.
Then they pass a kitchen—it's nice—and a bathroom—it's nice too—before ending up in the engine room.
And this, friends, is where it all goes down. This is how the Nautilus outmaneuvered the Abraham Lincoln. But it's so complex that Aronnax doesn't even try to understand how it all works.
He just wants to know how Nemo can steer the vessel, and how he can dive and resurface so easily.