Then of a sudden Dick knew! Those squares and parallelograms of bare ground indicated the foundations of buildings. He was looking down on the very site of the Invisible Emperor's stronghold!
He shouted, and pointed downward. Luke Evans looked round and nodded. He understood. He patted the camera-box with a grim smile on his old face.
CHAPTER VIII
The Magnetic Trap
pon those squares and oblongs of bare earth, incredible as it seemed, rose the structures of the Invisible Empire, themselves both invisible and transparent, so that one looked straight down through them and saw only the ground beneath them.
Every interior floor and girder must have been treated with the gas. They had been cunning. They must have discovered some permanent means of charging paint with the shadow-breaking gas, so that the buildings would remain invisible for months and years instead of hours.
But they had not been cunning enough. It had not occurred to them that the foundations would still be visible underneath, for the simple reason that grass does not grow without sunlight.
Dick saw old Luke Evans nodding and pointing downward. The old man picked up his end of the speaking-tube, but Dick ignored the gesture. He signaled to his flight to rise, and zoomed up, circling, and studying the land beneath.
That oblong was evidently the central building. Those four squares probably housed airplanes, and each would hold half a dozen. That elliptical building might contain a dirigible. That round patch was probably the gas factory.