"Then you have not yet completed your solution of the secret?" "Yes, I have; for I am as certain of the result as if I had seen it, but I thought you were entitled to be in with me at the death." From the nearest railway station we took horses to the laboratory, which occupied a secluded but most beautiful site at an elevation of about six thousand feet above sea-level. With considerable surprise I noticed a building surmounted with a dome, recalling what we had seen from the Grand Teton on the roof of Dr. Syx's mill. Hall, observing my look, smiled significantly, but said nothing. The laboratory proper occupied a smaller building adjoining the domed structure. Hall led the way into an apartment having but a single door and illuminated by a skylight. "This is my sanctum sanctorum," he said, "and you are the first outsider to enter it. Seat yourself comfortably while I proceed to unveil a little corner of the artemisium mystery." Near one end of the room, which was about thirty feet in length, was a table, on which lay a glass tube about two inches in diameter and thirty inches long. In the farther end of the tube gleamed a lump of yellow metal, which I took to be gold. Hall and I were seated near another table about twenty-five feet distant from the tube, and on this table was an apparatus furnished with a concave mirror, whose optical axis was directed towards the tube. It occurred to me at once that this apparatus would be suitable for experimenting with electric waves. Wires ran from it to the floor, and in the cellar beneath was audible the beating of an engine. My companion made an adjustment or two, and then remarked: "Now, keep your eyes on the lump of gold in the farther end of the tube yonder. The tube is exhausted of air, and I am about to concentrate upon the gold an intense electric influence, which will have the effect of making it a kind of kathode pole. I only use this term for the sake of illustration. You will recall that as long ago as the days of Crookes it was known that a kathode in an exhausted tube would project particles, or atoms, of its substance away in straight lines. Now watch!" I fixed my attention upon the gold, and presently saw it enveloped in a most beautiful violet light. This grew more intense, until, at times, it was blinding, while, at the same moment, the interior of the tube seemed to have become charged with a luminous vapor of a delicate pinkish hue. "Watch! Watch!" said Hall. "Look at the nearer end of the tube!" "Why, it is becoming coated with gold!" I exclaimed.