“What’s the difference between a biplane and a monoplane?” interposed Mr. Miles.
This was a puzzler for most of the boys. After several had answered and flunked, Hal Kenyon spoke up:
“A monoplane has one plane, and a biplane has two planes.”
“What is a plane?”
“A flat surface.”
“Good,” complimented Mr. Miles. “You know a little geometry. The planes are the wings of an aeroplane.
“Now, the aeroplane will be built on this plan: The part that will interest you boys most will be the cabin. As I said, it will carry two passengers comfortably besides the operator. And it is to be so arranged with an automatically shifting weight that these passengers can move about without disturbing the balance of the ship.
“This will really be an airship. The ordinary aeroplane is not entitled to such a name, for it is merely a skeleton without any body. This vessel will have a real body, made mostly of aluminum, except the glass windows and ports. The front, or prow, will be blunt in accord with the latest ideas of air friction. The front and rear of this cabin will be supplied with flexible slides that may be slipped around to the sides, leaving the front and rear open. This will remove practically all resistance, except for perpendicular rods six inches apart, giving the cabin something of the appearance of a cage.
“In cold weather, or in high altitudes, these slides can be closed and the cabin warmed with a small alcohol stove. Otherwise there will be little remarkable about the ship. You will all be interested in such details as the motor and the steering and weather apparatus. You will learn all about the altitude barometer and the anemometer, or speed measurer. In other words, you will absorb a lot of information on air navigation while putting this airship together.”
“How about that weight?” Hal questioned as the instructor in aeronautics paused. “You say it shifts automatically. Can you explain that so we can understand how it keeps the ship from turning over?”