“You wear the metal of a green warrior and are followed by a calot, yet you are of the figure of a red man. In color you are neither green nor red. In the name of the ninth day, what manner of creature are you?”

“I am a friend of the red men of Barsoom and I am starving. In the name of humanity open to us,” I replied.

Presently the door commenced to recede before me until it had sunk into the wall fifty feet, then it stopped and slid easily to the left, exposing a short, narrow corridor of concrete, at the further end of which was another door, similar in every respect to the one I had just passed. No one was in sight, yet immediately we passed the first door it slid gently into place behind us and receded rapidly to its original position in the front wall of the building. As the door had slipped aside I had noted its great thickness, fully twenty feet, and as it reached its place once more after closing behind us, great cylinders of steel had dropped from the ceiling behind it and fitted their lower ends into apertures countersunk in the floor.