An elevator is a car that can be moved up and down a shaft from one floor to an-other. The car has cables fastened to it at the top. These cables go over pulleys at the top of the shaft. To the other end of these cables a weight is fastened. This weight weighs about as much as the elevator car and is called a "counterweight." The counterweight makes it easier to lift the car. A person waiting for an elevator often sees the counterweight move past. As the elevator goes up, the counterweight moves down. When the elevator goes down, the counterweight moves up.
The earliest elevators were hydraulic. They were pushed up by water. Now most elevators are run by low-speed electric motors that operate the pulleys.
Some elevators are automatic. The rider simply pushes a button as he enters the car, and the car goes to the floor he wants.
If an elevator were to fall several floors, any people in it might be badly hurt. But there are special safety brakes to keep an elevator from falling.
Escalators, or moving stairways, are taking the place of elevators in some buildings. They take up more room than elevators and are not so fast. They are not likely to take the place of elevators in tall skyscrapers.
