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. [Illustration] [Illustration: LOOKING OUT OF INSPECTOR’S PIT AT CAR PASSING OVERHEAD] 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. [Illustration: BRAKEMAN UNCOUPLING CARS] Something does rise up like fingers from the sides of the track. It is the car retarder which squeezes against the wheels and keeps the car from rolling along too fast. The retarder works by electricity. The towerman just presses a button or a handle in the tower, and far down the track the retarder machinery goes to work. Before railroads had this machinery, brakemen went over the hump with the cars, working fast and hard to put the hand brakes on at just the right time. Brakemen who did this were called hump riders. Once in a while a hump rider still goes with a car of very fragile freight that might be broken if it banged into another car the least bit too hard. [Illustration: LOOKING DOWN INTO PIT AT THE INSPECTOR AND HIS SEARCHLIGHTS--] Car after car drifts down the hump and stops just where it should. When one freight train has been unscrambled, another rolls up beneath the tower, and its cars, too, are shuffled. In just a few hours half a dozen trains have been broken up and made into new ones. Some yards have extra inspectors who stand on top of a building and look down at the cars from above. They can see broken parts that the man in the inspection pit might miss. In other yards, a man is stationed beside the track that leads up to the hump. In his hands, he holds something that looks like a gun. It is--an oil gun. As each car passes, he takes aim and fires a stream of oil straight into the car’s journal box. (You’ll read about the journal box on page 42.) [Illustration]