We just learned about the Firebox on a locomotive.
Another part of a steam locomotive is the Boiler.
We learned before about the Fire Tube Boiler that has a bunch of tubes full of water that are heated up by the burning coal in the Firebox.
The boiler is the long cylinder shaped part of the locomotive that has all of that fire burning and hot water heating inside of it.
(from: wikipedia - boiler)
Kid Facts - Blast from the past: Valve Body