“I can testify to that,” said Mr. Ogden.
“Perhaps a short description of the air-ship may interest you,” added Major Carroll, “so, while Mr. Ogden and myself are conferring together, I’ll have Kindale—he’s my chief mechanician—supply it.”
Bob thanked him.
“Yes siree; the ‘Border City’ flies like an eagle,” said Kindale, a moment later. “How long is the balloon? About a hundred an’ fifty feet. The diameter’s a bit less’n forty. You see, like some rowboats, one end is sharply pointed, an’ t’other’s round, so as to give less resistance to the air.”
As the two walked slowly along by the side of the huge air-ship Bob Somers marveled at the knowledge and skill which had been able to produce such a wonderful piece of work. The long car, attached to the keel by wire cables, was completely enclosed with rubber cloth, having mica-covered windows at the front and rear ends and an entrance in the middle.
“The bag is made o’ several thicknesses o’ rubber-coated fabric,” explained Kindale. “Of course you know the whole thing ain’t filled with gas?”
“I believe the bag is divided into compartments,” said Bob.
“Sure; an’ the reason is this: cold, or air pressure, contracts the gas, while heat, or lessening of the air pressure, causes it to expand. Therefore, if we ascend to a very high altitude the gas expands considerably; an’ supposin’ it’s on a blazin’ hot day—why, then the envelope stands a good chance o’ bustin’, doesn’t it?”
“Certainly!” responded Bob.
“Well, one o’ the compartments is really a little balloon inside the big one; an’ it’s kept filled with air by a motor—just pressure enough to balance the pressure of the gas around it.”