Perhaps you wonder how it is possible to teach sheep to do this kind of job. The answer is that they get a treat every time they finish loading a car. Some pets like sugar or a carrot, but these two were fondest of a big piece of chewing tobacco. [Illustration] Stock cars for sheep and pigs have two decks. Cars for cattle and horses and mules have only one. And poultry cars have several. The slits in livestock cars let in plenty of fresh air and keep the animals cool. Since pigs are likely to suffer from heat on a trip, they often get a soaking bath before they go into the cars. There is a rule that animals must not travel more than a day and a half cooped up in a car. So trains stop at resting pens along the way to let the animals out for exercise and food and water. After a few hours they are loaded again. Meantime the cars have had fresh clean sand or straw spread around on the floor. Some very fast stock trains zoom along at such high speed that they reach the market before the animals need to stop and rest. Veterinaries and inspectors often work at stock stations, looking out for animals that are sick. Caretakers for poultry and animals usually go along in the caboose. TANK CARS [Illustration] Railroaders call a tank car a can. It really is an enormous can with different kinds of lining for hauling different liquids. Milk tanks have glass or steel linings. Tanks for certain chemicals are lined with rubber or aluminum or lead. [Illustration] Altogether there are more than two hundred types of tank car, and here are some of the things that travel in them: fuel oil, gasoline, and asphalt; molasses and sugar syrup; turpentine and alcohol; lard, corn oil and fish oil for vitamins. [Illustration] Some tank cars have heating coils that warm up lard or molasses and keep it from getting too stiff to flow out easily. Most tank cars have a dome on top. If they didn’t, they might burst open at the seams when the liquid inside them begins to expand in hot weather. Instead, the liquid bulges up into the dome, and no harm is done. [Illustration] Wine tank cars have four compartments for carrying different kinds of wine. [Illustration] Milk tank cars are built with two compartments that tip slightly toward the center so that every bit of milk will flow out. Each compartment is rather like a thermos bottle, with special wrapping around it to keep the milk from getting warm and sour. And the tanks are always filled brim full so the milk won’t slosh around and churn up a batch of butter on the road. Can you guess why milk tanks don’t need domes? Remember the milk must stay cool. Even when the sun is hot outside, the cool milk doesn’t expand, so no dome is needed to keep the tank from bursting. [Illustration] HOPPERS AND GONDOLAS