stopped, and with its stoppage the light faded and soon disappeared. The next day Dr. Syx gave it out that on starting up his engine in the night something had caught fire, which compelled him immediately to shut down again. The few who had seen the light, with the exception of your humble servant, accepted the doctor's explanation without a question. But I knew there had been no fire, and Syx's anxiety to spread the lie led me to believe that he had narrowly escaped giving away a vital secret. I said nothing about my suspicions, but upon inquiry I found out that an extra and pressing order for metal had arrived from the Austrian government the very day of the pretended fire, and I drew the inference that Syx, in his haste to fill the order—his supply having been drawn low—had started to work, contrary to his custom, at night, and had immediately found reason to repent his rashness. Of course, I connected the strange light with this sudden change of mind.
"My suspicions having been thus stimulated, and having been directed in a certain way, I began, from that moment to notice closely the hours during which the engine labored. At night it was always quiet, except on that one brief occasion. Sometimes it began early in the morning and stopped about noon. At other times the work was done entirely in the afternoon, beginning sometimes as late as three or four o'clock, and ceasing invariably at sundown. Then again it would start at sunrise and continue the whole day through.
"For a long time I was unable to account for these eccentricities, and the problem was not rendered much clearer, although a startling suggestiveness was added to it, when, at length, I noticed that the periods of activity of the engine had a definite relation to the age of the moon. Then I discovered, with the aid of an almanac, that I could predict the hours when the engine would be busy. At the time of new moon it worked all day; at full moon, it was idle; between full moon and last quarter, it labored in the forenoon, the length of its working hours increasing as the quarter was approached; between last quarter and new moon, the hours of work lengthened, until, as I have said, at new moon they lasted all day; between new moon and first quarter, work began later and later in the forenoon as the quarter was approached, and between first quarter and full moon the laboring hours rapidly shortened, being confined to the latter part of the afternoon, until at full moon complete silence reigned in the mill."
The Moon Is Concerned in Dr. Syx's Mystery
"WELL! well!" I broke in, greatly astonished by Hall's singular recital, "you must have thought Dr. Syx was a cross between an alchemist and an astrologer."
"Note this," said Hall, disregarding my interruption, "the hours when the engine worked were invariably the hours during which the moon was above the horizon!"
"What did you infer from that?"
"Of course, I inferred that the moon was directly concerned in the mystery; but how? That bothered me for a long time, but a little light broke into my mind when I picked up, on the mountain-side, a dead bird, whose scorched feathers were bronzed with artemisium, and sometime later another similar victim of a mysterious form of death. Then came the attack on the mine and its tragic finish. I have already told you what I observed on that occasion. But, instead of helping to clear up the mystery, it rather complicated it for a time. At length, however, I reasoned my way partly out of the difficulty. Certain things which I had noticed in the Syx mill convinced me that there was a part of the building whose existence no visitor suspected, and, putting one thing with another, I inferred that the roof must be open above that secret part of the structure, and that if I could get upon a sufficiently elevated place I could see something of what was hidden there.
"At this point in the investigation I proposed to you the trip to the top of the Teton, the result of which you remember. I had calculated the angles with great care, and I felt certain that from the apex of the mountain I should be able to get a view into the concealed chamber, and into just that side of it which I wished particularly to inspect. You remember that I called your attention to a shining object underneath the circular opening in the roof. You could not make out what it was, but I saw enough to convince me that it was a gigantic parabolic mirror. I'll show you a smaller one of the same kind presently.
"Now, at last, I began to perceive the real truth, but it was so wildly incredible, so infinitely remote from all human experience, that I hardly ventured to formulate it, even in my own secret mind. But I was bound to see the thing through to the end. It occurred to me that I could prove the accuracy of my theory with the aid of a kite. You were kind enough to lend your assistance in that experiment, and it gave me irrefragable evidence of the existence of a shaft of flying atoms extending in a direct line between Dr. Syx's pretended mine and the moon!"
"Hall!" I exclaimed, "you are mad!"
My friend smiled good-naturedly, and went on with his story.
Why the Kite Was Burned
THE instant the kite shrivelled and disappeared I understood why the works were idle when the moon was not above the horizon, why birds flying across that fatal beam fell dead upon the rocks, and whence the terrible master of that mystery mill derived the power of destruction that could wither an army as the Assyrian host in Byron's poem:
"Melted like snow in the glance of the Lord."
"But how did Dr. Syx turn the flying atoms against his enemies?" I asked.
"In a very simple manner. He had a mirror mounted so that it could be turned in any direction, and would shunt the stream of metallic atoms, heated by their friction with the air, towards any desired point. When the attack came he raised this machine above the level of the roof and swept the mob to a lustrous, if expensive, death."
"And the light at night—"
"Was the shining of the heated atoms, not luminous enough to be visible in broad day, for which reason the engine never worked at night, and the
