"We talked it over carefully," he went on, "bringing to bear all our power of analysis and habit of calm, scientific thought. We considered minutely the time element in the phenomena. Although the deep chanting began at the very moment of moonrise, fully five minutes had passed between its full lifting and the strange sighing sound from the inner terrace. I went back in memory over the happenings of the night before. At least ten minutes had intervened between the first heralding sigh and the intensification of the moonlight in the courtyard. And this glow grew for at least ten minutes more before the first burst of the crystal notes. Indeed, more than half an hour must have elapsed, I calculated, between the moment the moon showed above the horizon and the first delicate onslaught of the tinklings.
"'Edith!' I cried. 'I think I have it! The grey rock opens five minutes after upon the moonrise. But whoever or whatever it is that comes through it must wait until the moon has risen higher, or else it must come from a distance. The thing to do is not to wait for it, but to surprise it before it passes out the door. We will go into the inner court early. You will take your rifle and pistol and hide yourself where you can command the opening—if the slab does open. The instant it opens I will enter. It's our best chance, Edith. I think it's our only one.'
"My wife demurred strongly. She wanted to go with me. But I convinced her that it was better for her to stand guard without, prepared to help me if I were forced again into the open by what lay behind the rock.
"At the half-hour before moonrise we went into the inner court. I took my place at the side of the grey rock. Edith crouched behind a broken pillar twenty feet away; slipped her rifle-barrel over it so that it would cover the opening.
"The minutes crept by. The darkness lessened and through the breaches of the terrace I watched the far sky softly lighten. With the first pale flush the silence of the place intensified. It deepened; became unbearably—expectant. The moon rose, showed the quarter, the half, then swam up into full sight like a great bubble.
"Its rays fell upon the wall before me and suddenly upon the convexities I have described seven little circles of light sprang out. They gleamed, glimmered, grew brighter—shone. The gigantic slab before me glowed with them, silver wavelets of phosphorescence pulsed over its surface and then—it turned as though on a pivot, sighing softly as it moved!
"With a word to Edith I flung myself through the opening. A tunnel stretched before me. It glowed with the same faint silvery radiance. Down it I raced. The passage turned abruptly, passed parallel to the walls of the outer courtyard and then once more led downward.
"The passage ended. Before me was a high vaulted arch. It seemed to open into space; a space filled with lambent, coruscating, many-coloured mist whose brightness grew even as I watched. I passed through the arch and stopped in sheer awe!
"In front of me was a pool. It was circular, perhaps twenty feet wide. Around it ran a low, softly curved lip of glimmering silvery stone. Its water was palest blue. The pool with its silvery rim was like a great blue eye staring upward.
"Upon it streamed seven shafts of radiance. They poured down upon the blue eye like cylindrical torrents; they were like shining pillars of light rising from a sapphire floor.