"No," said Hall, "I must carefully choose the point on the lunar surface where to operate. But that will present no difficulty. I made up my mind as soon as I had penetrated Syx's secret that he obtained the metal from those mystic white streaks which radiate from Tycho, and which have puzzled the astronomers ever since the invention of telescopes. I now believe those streaks to be composed of immense veins of the metal that Syx has most appropriately named artemisium, which you, of course, recognize as being derived from the name of the Greek goddess of the moon, Artemis, whom the Romans called Diana. But now to work!" It was less than a day past the time of new moon, and the earth's satellite was too near the sun to be visible in broad daylight. Accordingly, the mirror had to be directed by means of knowledge of the moon's place in the sky. Driven by accurate clockwork, it could be depended upon to retain the proper direction when once set. With breathless interest I watched the proceedings of my friend and his assistants. The strain upon the nerves of all of us was such as could not have been borne for many hours at a stretch. When everything had been adjusted to his satisfaction, Hall stepped back, not without betraying his excitement in flushed cheeks and flashing eyes, and pressed a lever. The powerful engine underneath the floor instantly responded. The experiment was begun. "I have set it upon a point about a hundred miles north of Tycho, where the Yerkes photographs show a great abundance of the white substance," said Hall. Then we waited. A minute elapsed. A bird, fluttering in the opening above, for a second or two, wrenched our strained nerves. Hall's face turned pale. "They had better keep away from here," he whispered, with a ghastly smile. Two minutes! I could hear the beating of my heart. The engine shook the floor. Three minutes! Hall's face was wet with perspiration. The bird blundered in and startled us again. Four minutes! We were like statues, with all eyes fixed on the polished ball of silver, which shone in the brilliant light concentrated upon it by the mirror. Five minutes! The shining ball had become a confused blue, and I violently winked to clear my vision. "At last! Thank God! Look! There it is!" It was Hall who spoke, trembling like an aspen. The silver knob had changed color. What seemed a miniature rainbow surrounded it, with concentric circles of blinding brilliance. Then something dropped flashing into an earthen dish set beneath the ball! Another glittering drop followed, and, at a shorter interval, another!