The towerman sits in a tower beside the track at the top of a little hill called the hump. The main track goes over the hump and down. Then it divides into several branch tracks. If you uncouple a car just at the top of the hump, it will roll down the slope by itself.
To make the car go onto the right branch, the towerman works an electric switch. He just pushes little handles on the board in front of him, and electric machinery moves the switches in the tracks.
On the desk beside him, the towerman has a list that tells him where each car in the train is and what city it is headed for. He knows which branch tracks should be used—track number 4 for cars going to Baltimore, track 6 for Chicago cars.
Slowly the switch engine pushes the train toward the hump. On the way the cars pass over a big hole underneath the track. In the hole sits a man in a chair that can be tipped and turned. And all around are bright lights that shine on the undersides of cars as they pass. This is the inspection pit. The man in the chair tilts this way and that, watching through a shatterproof glass hood to see if anything is broken or loose on the under side of the cars. When he spots a car that needs repairing, he talks with the towerman by radio telephone. And the towerman switches the car off to a repair track.
(Not all yards have radio telephone. In the ones that don’t, the inspector pushes a button and squirts whitewash onto a car to mark it for repair.)
Now the cars come close to the hump. A brakeman uncouples the first one. Slowly it starts downhill. Then it gathers speed—faster, faster. If it hits another car there will be a crash. But, like magic, something seems to grab at the wheels and slow them down.
