“They are placed at intervals of fifty miles,” returned the other.
“Then, that light away down near the horizon is nearly 150 miles from us?”
“Yes.”
“And our elevation now is 10,000 feet, you say?”
“So I observed it, as I told you, some fifteen or twenty minutes ago.”
Then, after a moment’s silence, Cobb exclaimed: “We are rising. We cannot be less than 12,500 feet above the ocean.”
“How do you make that out, Junius?” asked Hugh. “I don’t think we have ascended 2,500 feet since my last observation.”
“It is easily answered,” said the other. “The curvature of the earth and the refraction of light necessitate an elevation of 1,430 feet for one to see an object on the surface at a distance of fifty miles. To see this light, distant 150 miles, our altitude must be at least 11,500 feet.”
“Yes?”