“We’d have to have nonskid chains and brakes on our feet to tackle that,” mused Larry. Abstractedly be ran his hands over the edge on which he was leaning. Suddenly they hesitated and then gripped tightly.

“That’s a queer one!” he exclaimed. His right palm was resting upon a rounded protuberance, on the side of which were three small circular indentations.

“A queer one⁠—” he repeated⁠—and pressed his fingers upon the circles.

There was a sharp click; the slabs that had opened to let us through swung swiftly together; a curiously rapid vibration thrilled through us, a wind arose and passed over our heads⁠—a wind that grew and grew until it became a whistling shriek, then a roar and then a mighty humming, to which every atom in our bodies pulsed in rhythm painful almost to disintegration!

The rosy wall dwindled in a flash to a point of light and disappeared!