The early balloons consisted of an inflated bag to which an open basket, or gondola,was attached by ropes. To make the balloon go higher into the air, the "pilot" lightened its weight by dropping bags of sand, which were secured to the sides of the gondola. To make, the balloon descend, he opened a valve and let some of the gas escape. The balloon rose into the air, but there was no way to control its flight. Once aloft, the balloon — and the men with it — were at the mercy of the winds.
The dirigible, or air-ship as it is sometimes called, can be steered. It consists of an elongated, gas-filled bag with cars, or gondolas, below for passengers and power. The dirigible takes advantage of the wind, but also uses motor-driven propellers. The early dirigibles used a sliding weight to make them go up or down. Pushing the weight toward the front pointed the nose of the airship down; conversely, with the weight toward the back, the nose pointed upward. Later dirigibles used horizontal tail fins to direct their upward and downward movement. Vertical tail fins were used to steer them right and left.
