The Poisoned Pen

by Arthur B. Reeve

Prescott, with one hand on my arm and the other on Dr. Burnham's, was moving toward the door.

"One moment, Prescott," interrupted Kennedy, detaining him with a look. "There was something I was about to say when Dr. Burnham's urgent message prevented it. I did not take the trouble even to find out how you obtained that little globule of molten gold from the crucible of alleged copper. There are so many tricks by which the gold could have been 'salted' and brought forth at the right moment that it was hardly worth while. Besides, I had satisfied myself that my first suspicions were correct. See that?"

He held out the little piece of mineral I had already seen in his hand in the alchemist's laboratory.

"That is a piece of willemite. It has the property of glowing or fluorescing under a certain kind of rays which are themselves invisible to the human eye. Prescott, your story of the transmutation of elements is very clever, but not more clever than your real story. Let us piece it together. I had already heard from Dr. Burnham how Mr. Haswell was induced by his desire for gain to visit you and how you had most mysteriously predicted his blindness. Now, there is no such thing as telepathy, at least in this case. How then was I to explain it? What could cause such a catastrophe naturally? Why, only those rays invisible to the human eye, but which make this piece of willemite glow - the ultra-violet rays."

Kennedy was speaking rapidly and was careful not to pause long enough to give Prescott an opportunity to interrupt him.

"These ultra-violet rays," he continued, "are always present in an electric arc light though not to a great degree unless the carbons have metal cores. They extend for two octaves above the violet of the spectrum and are too short to affect the eye as light, although they affect photographic plates. They are the friend of man when he uses them in moderation as Finsen did in the famous blue light treatment. But they tolerate no familiarity. To let them -=20 particularly the shorter of the rays - enter the eye is to invite trouble. There is no warning sense of discomfort, but from six to eighteen hours after exposure to them the victim experiences violent pains in the eyes and headache. Sight may be seriously impaired, and it may take years to recover. Often prolonged exposure results in blindness, though a moderate exposure acts like a tonic. The rays may be compared in this double effect to drugs, such as strychnine. Too much of them may be destructive even to life itself."

Prescott had now paused and was regarding Kennedy contemptuously. Kennedy paid no attention, but continued: "Perhaps these mysterious rays may shed some light on our minds, however. Now, for one thing, ultra-violet light passes readily through quartz, but is cut off by ordinary glass, especially if it is coated with chromium. Old Mr. Haswell did not wear glasses. Therefore he was subject to the rays - the more so as he is a blond, and I think it has been demonstrated by investigators that blonds are more affected by them than are brunettes.

"You have, as a part of your machine, a peculiarly shaped quartz mercury vapour lamp, and the mercury vapour lamp of a design such as that I saw has been invented for the especial purpose of producing ultra-violet rays in large quantity. There are also in your machine induction coils for the purpose of making an impressive noise, and a small electric furnace to heat the salted gold. I don't know what other ingenious fakes you have added. The visible bluish light from the tube is designed, I suppose, to hoodwink the credulous, but the dangerous thing about it is the invisible ray that accompanies that light. Mr. Haswell sat under those invisible rays, Prescott, never knowing how deadly they might be to him, an old man.

"You knew that they would not take effect for hours, and hence you ventured the prediction that he would be stricken at about midnight. Even if it was partial or temporary, still you would be safe in your prophecy. You succeeded better than you hoped in that part of your scheme. You had already prepared the way by means of a letter sent to Mr. Haswell through Dr. Burnham. But Mr. Haswell's credulity and fear worked the wrong way. Instead of appealing to you he hated you. In his predicament he thought only of his banished daughter and turned instinctively to her for help. That made necessary a quick change of plans."

Prescott, far from losing his nerve, turned on us bitterly. "I knew you two were spies the moment I saw you," he shouted. "It seemed as if in some way I knew you for what you were, as if I knew you had seen Mr. Haswell before you came to me. You, too, would have robbed an inventor as I am sure he would. But have a care, both of you. You may be punished also by blindness for your duplicity. Who knows?"