If my theory of the grey slab's mechanism were correct, it was practically certain that with the satellite only a few nights past the full we could concentrate enough light on the bosses to open the rock. And as the ray streams through the seven globes described by Throckmartin would be too weak to energize the Pool, we could enter the chamber free from any fear of encountering its tenant, make our preliminary observations and go forth before the moon had dropped so far that the concentration in the condensers would fall below that necessary to keep the portal from closing.
I took out also a small spectroscope, and a few other instruments for the analysis of certain light manifestations and the testing of metal and liquid. Finally, I put aside my emergency medical kit.
I had hardly finished examining and adjusting these before O'Keefe and Huldricksson returned. They reported signs of a camp at least ten days old beside the northern wall of the outer court, but beyond that no evidence of others beyond ourselves on Nan-Tauach.
We prepared supper, ate and talked a little, but for the most part were silent. Even Larry's high spirits were not in evidence; half a dozen times I saw him take out his automatic and look it over. He was more thoughtful than I had ever seen him. Once he went into the tent, rummaged about a bit and brought out another revolver which, he said, he had got from Da Costa, and a half-dozen clips of cartridges. He passed the gun over to Olaf.
At last a glow in the southeast heralded the rising moon. I picked up my instruments and the medical kit; Larry and Olaf shouldered each a short ladder that was part of my equipment, and, with our electric flashes pointing the way, walked up the great stairs, through the enclosures, and straight to the grey stone.
By this time the moon had risen and its clipped light shone full upon the slab. I saw faint gleams pass over it as of fleeting phosphorescence—but so faint were they that I could not be sure of the truth of my observation.
We set the ladders in place. Olaf I assigned to stand before the door and watch for the first signs of its opening—if open it should. The Becquerels were set within three-inch tripods, whose feet I had equipped with vacuum rings to enable them to hold fast to the rock.
I scaled one ladder and fastened a condenser over the boss; descended; sent Larry up to watch it, and, ascending the second ladder, rapidly fixed the other in its place. Then, with O'Keefe watchful on his perch, I on mine, and Olaf's eyes fixed upon the moon door, we began our vigil. Suddenly there was an exclamation from Larry.
"Seven little lights are beginning to glow on this stone!" he cried.
But I had already seen those beneath my lens begin to gleam out with a silvery lustre. Swiftly the rays within the condenser began to thicken and increase, and as they did so the seven small circles waxed like stars growing out of the dusk, and with a queer—curdled is the best word I can find to define it—radiance entirely strange to me.