There was no mistaking it. This was, in very deed, the portal through which Throckmartin had seen pass that gloriously dreadful apparition he called the Dweller. At its base was the curious, seemingly polished cup-like depression within which, my lost friend had told me, the opening door swung.
What was that portal—more enigmatic than was ever sphinx? And what lay beyond it? What did that smooth stone, whose wan deadness whispered of ages-old corridors of time opening out into alien, unimaginable vistas, hide? It had cost the world of science Throckmartin's great brain—as it had cost Throckmartin those he loved. It had drawn me to it in search of Throckmartin—and its shadow had fallen upon the soul of Olaf the Norseman; and upon what thousands upon thousands more I wondered, since the brains that had conceived it had vanished with their secret knowledge?
What lay beyond it?
I stretched out a shaking hand and touched the surface of the slab. A faint thrill passed through my hand and arm, oddly unfamiliar and as oddly unpleasant; as of electric contact holding the very essence of cold. O'Keefe, watching, imitated my action. As his fingers rested on the stone his face filled with astonishment.
"It's the door?" he asked. I nodded. There was a low whistle from him and he pointed up toward the top of the grey stone. I followed the gesture and saw, above the moon door and on each side of it, two gently curving bosses of rock, perhaps a foot in diameter.
"The moon door's keys," I said.
"It begins to look so," answered Larry. "If we can find them," he added.
"There's nothing we can do till moonrise," I replied. "And we've none too much time to prepare as it is. Come!"
A little later we were beside our boat. We lightered it, set up the tent, and as it was now but a short hour to sundown I bade them leave me and make their search. They went off together, and I busied myself with opening some of the paraphernalia I had brought with me.
First of all I took out the two Becquerel ray-condensers that I had bought in Sydney. Their lenses would collect and intensify to the fullest extent any light directed upon them. I had found them most useful in making spectroscopic analysis of luminous vapours, and I knew that at Yerkes Observatory splendid results had been obtained from them in collecting the diffused radiance of the nebulae for the same purpose.