Sixty freight cars have come roaring together over the mountains behind Sam’s engine. But now the cars have to be separated. Some of them are going to Baltimore. Some will turn north to Chicago. Others are bound south. Freight cars for twenty different cities are coupled together in one train, and somebody must unscramble them.

Suppose you have a lot of colored beads on a string and you want to separate them into greens and reds and blues. The easiest way is to get three cups and let the beads drop off one by one, each into its own cup with the others of the same color.

That’s just what railroaders do with a freight train. Instead of cups, of course, they have a lot of separate tracks, all branching off a main track. On one branch track, they collect the cars that go to Baltimore; on another, the cars for Chicago; on another, the cars headed south. This system of tracks is a classification yard.

In order to turn the cars from one track to another, there must be a lot of switches. A switch is made up of movable pieces of rail that guide the cars’ wheels. Look at the picture and you will see how a switch guides a car either along the main track or onto a branch track that curves off to the right.

Some of the most wonderful inventions in the world have been put to work in the big freight classification yards. First the regular engine leaves the train and a special switch engine couples on. The engineer of the switch engine has a radio telephone in the cab, so he can listen to orders from the towerman who unscrambles the train.

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.

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.

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.)

Not every freight yard has a hump or car retarders or radio telephones. Only the biggest ones have all these things. In many yards the switch engine pushes the whole train first onto one track and then onto another, dropping a car each time.

There are several kinds of switch engine, built especially for their jobs. But switching is often done with very old engines that aren’t fast enough for regular runs any more. Railroad men call an old wheezy engine a teakettle. An ordinary switch engine is a bobtail or a yard goat.

If the yard doesn’t have switches that work by electricity, switchmen work them by hand. A switchman is sometimes called a cherry picker, because of the red lights on the switches. Another nickname for him is snake. That’s because he used to wear a union button with a big snaky S on it. Many railroaders belong to unions called Brotherhoods. Part of the safety of their work was brought about by the unions which helped to get laws passed and rules established to make railroading as free from danger as possible.

In the old days, one great danger came from the big, heavy gadget called a link-and-pin that joined the cars together. The switchman or the brakeman had to reach in and fasten it when a train was being made up. If the cars began to move while he was at work, he might get his fingers cut off.

All cars now have automatic couplings which clasp together and hold tight when one car bumps another. To uncouple, the switchman works a handle that keeps his fingers safely out of the way.

A railroad yard is a noisy place. Usually the engineer can’t possibly talk with a switchman down the track, no matter how loud he shouts. So railroaders have worked out a whole sign language in which they can talk to each other from a distance. The pictures tell what some of these special signals mean.

After a new freight train has been made up at the classification yard, a car inspector puts a blue flag on the engine and another on the caboose. Then he checks up carefully on the whole train to make sure everything is in good working order. An old nickname for inspector is car toad, because he often squats down to look for broken parts. While he is at work, the blue flags are a warning that the train must not be disturbed. If the inspector finds a car that needs repairs, he reports that it is a “bad order car.”