“Just this,” I replied. “As you may have seen, I held that letter to the light under a reading glass, which acted as a burning glass, for some minutes. I was looking for invisible ink, which could be brought out by heating. I didn’t find any, but as I turned away, the paper came for a moment into the shadow and I saw a slight gleam like the glimmer of phosphorescence on water. Now last year I met an old scientist, Von Meyren, who happened to mention that he had found that certain inks which had been used for parchments in olden times held a substance which becomes phosphorescent when exposed to radium. He got a second letter in that way once, from beneath a message one of the Popes sent to a king of France. You see parchment was and is expensive, and hard to get. They used the same piece over and over again, removing the old inks by scraping or dissolving. Somehow the radium brought out the stuff that had been apparently removed. When Reid said ‘Papal Bulls’ it gave me an idea. It is barely possible that the man who wrote the letter might have written something on that piece of parchment before and then erased it. I thought I’d try radium on the chance. There may be nothing in it, but it will do no harm, will it, Miss Haldane?” “Oh, no,” said Miss Haldane. “I have some of my brother’s radium right here. I’ll bring it down and we’ll expose the letter to it.” A moment later she returned, this time with her cousin Mrs. Hartnell. “Now we will darken the room,” she said, holding out a small lead case with hinged cover, “and try this wonder worker. But you must not move from your places. If you get in the way of the rays, you are likely to be badly burned.” We were grouped in a semi-circle before a bared table whereon was placed the open letter in a holder, confronted with the leaden casket. I was given the place of honor, directly in front, and Miss Haldane put her chair beside mine. Carefully she opened the hinged door in the front of the radium holder, stepped to the switch, threw off the electric light, and came to sit beside me. We waited in perfect silence, our eyes bent on the blackness before us. I could hear her regular breathing, I could feel the brush of her skirt as she leaned forward, and I forgot all else,--the noise of the city without, the audience within, both disappeared from my consciousness. There was but a vast rolling ocean of blackness, and she and I, bound by a swiftly tightening chain, were being dragged closer and closer together. Old Von Meyren’s pet saying, “Love! Pah! What is it but an excess of positive electrons in a certain man, urging him towards the negative electrons in a certain woman?” kept ringing in my ears, the while I indignantly refuted it. Again and again it persisted, and with it came the thought that the waves from the radium were the chain which bound us.