We just learned about the Sand Dome.
Another part of steam locomotives is the Air Brakes.
When the engineer wants to stop the train, he pulls a lever to use the brakes.
The lever opens up something called an air reservoir which is a place where high pressured air is stored.
It is kind of like a really tight balloon filled with air, and opening it up causes the air to come blowing out.
The air goes through some tubes to get to a piece of metal called the brake shoe, and the air pressure pushes the metal brake shoe up against the wheel to stop the train.
(from: wikipedia - railway air brake)
Kid Facts - Blast from the past: Rotor