and was holding two black rubber disks to his ears.
At last the sound from overhead became articulate. It was weird, uncanny. Suddenly a voice said distinctly: "Let American dollars beware. They will not protect American daughters."
Craig had dropped the two ear-pieces and was gazing intently at the Osram lamp in the ceiling. Was he, too, crazy?
"Here, Mr. Brixton, take these two receivers of the detectaphone," said Kennedy. "Tell me whether you can recognise the voice."
"Why, it's familiar," he remarked slowly. "I can't place it, but I've heard it before. Where is it? What is this thing, anyhow?"
"It is some one hidden in the storeroom in the basement," answered Craig. "He is talking into a very sensitive telephone transmitter and—"
"But the voice—here?" interrupted Brixton impatiently.
Kennedy pointed to the incandescent lamp in the ceiling. "The incandescent lamp," he said, "is not always the mute electrical apparatus it is supposed to be. Under the right conditions it can be made to speak exactly as the famous 'speaking-arc,' as it was called by Professor Duddell, who investigated it. Both the arc-light and the metal-filament lamp can be made to act as telephone receivers."
It seemed unbelievable, but Kennedy was positive. "In the case of the speaking-arc or 'arcophone,' as it might be called," he continued, "the fact that the electric arc is sensitive to such small variations in the current over a wide range of frequency has suggested that a direct-current arc might be used as a telephone receiver. All that is necessary is to superimpose a microphone current on the main arc current, and the arc reproduces sounds and speech distinctly, loud enough to be heard several feet. Indeed, the arc could be used as a transmitter, too, if a sensitive receiver replaced the transmitter at the other end. The things needed are an arc-lamp, an impedance coil, or small transformer-coil, a rheostat, and a source of energy. The alternating current is not adapted to reproduce speech, but the ordinary direct current is. Of course, the theory isn't half as simple as the apparatus I have described."
He had unscrewed the Osram lamp. The talking ceased immediately.
"Two investigators named Ort and Bidger have used a lamp like this as a receiver," he continued. "They found that words spoken were reproduced in the lamp. The telephonic current variations superposed on the current passing through the lamp produce corresponding variations of heat in the filament, which are radiated to the glass of the bulb, causing it to expand and contract proportionately, and thus transmitting vibrations to the exterior air. Of course, in sixteen- and thirty-two-candle-power lamps the glass is too thick, and the heat variations are too feeble."
Who was it whose voice Brixton had recognised as familiar over Kennedy's hastily installed detectaphone? Certainly he must have been a scientist of no mean attainment. That did not surprise me, for I realised that from that part of Europe where this mystical Red Brotherhood operated some of the most famous scientists of the world had sprung.
A hasty excursion into the basement netted us nothing. The place was deserted.
We could only wait. With parting instructions to Brixton in the use of the detectaphone we said good night, were met by a watchman and escorted as far as the lodge safely.
Only one remark did Kennedy make as we settled ourselves for the long ride in the accommodation train to the city. "That warning means that we have two people to protect—both Brixton and his daughter."
Speculate as I might, I could find no answer to the mystery, nor to the question, which was also unsolved, as to the queer malady of Brixton himself, which his physician diagnosed as jaundice.
Chapter VI
The Detectaphone
Far after midnight though it had been when we had at last turned in at our apartment, Kennedy was up even earlier than usual in the morning. I found him engrossed in work at the laboratory.
"Just in time to see whether I'm right in my guess about the illness of Brixton," he remarked, scarcely looking up at me.
He had taken a flask with a rubber stopper. Through one hole in it was fitted a long funnel; through another ran a glass tube, connecting with a large U-shaped drying-tube filled with calcium chloride, which in turn connected with a long open tube with an up-turned end.
Into the flask Craig dropped some pure granulated zinc coated with platinum. Then he covered it with dilute sulphuric acid through the funnel tube. "That forms hydrogen gas," he explained, "which passes through the drying-tube and the ignition-tube. Wait a moment until all the air is expelled from the tubes."
He lighted a match and touched it to the open upturned end. The hydrogen, now escaping freely, was ignited with a pale-blue flame.
Next, he took the little piece of wall-paper I had seen him tear off in the den, scraped off some powder from it, dissolved it, and poured it into the funnel-tube.
Almost immediately the pale, bluish flame turned to bluish white, and white fumes were formed. In the ignition-tube a sort of metallic deposit appeared. Quickly he made one test after another. I sniffed. There was an unmistakable smell of garlic in the air.
"Arseniureted hydrogen," commented Craig. "This is the Marsh test for arsenic. That wall-paper in Brixton's den has been loaded down with arsenic, probably Paris green or Schweinfurth green, which is aceto-arsenite of copper. Every minute he is there he is breathing arseniureted hydrogen. Some one has contrived to introduce free hydrogen into the intake of his ventilator. That acts on the arsenic compounds in the wall-paper and hangings and sets free the gas. I thought I knew the smell the moment I got a whiff of it. Besides, I could tell by the jaundiced look of his face that he was being poisoned. His liver was out of order, and arsenic seems to accumulate in the liver."
"Slowly poisoned by minute quantities of gas," I repeated in amazement. "Some one in that Red Brotherhood is a diabolical genius. Think of it—poisoned wall-paper!"
It was still early in the forenoon when Kennedy excused himself, and leaving me to my own devices disappeared on one of his excursions into the underworld of the foreign settlements on the East Side. About the middle of the afternoon he reappeared. As far as I could learn all that he had found out was that the famous, or rather infamous, Professor Michael Kumanova, one of the leaders of the Red Brotherhood, was known to be somewhere in this country.
We lost no time in returning again to Woodrock late that afternoon. Craig hastened to warn Brixton of his peril from the contaminated atmosphere of the den, and at once a servant was set to work with a vacuum cleaner.
Carefully Craig reconnoitred the basement where the eavesdropping storeroom was situated. Finding it deserted, he quickly set to work connecting the two wires of the general household telephone with what looked very much like a seamless iron tube, perhaps six inches long and three inches in diameter. Then he connected the tube also with the private wire of Brixton in a similar manner.
"This is a special repeating-coil of high efficiency," he explained in answer to my inquiry. "It is absolutely balanced as to resistance, number of turns, and everything. I shall run this third line from the coil into Brixton's den, and then, if you like, you can accompany me on a little excursion down to the village where I am going to install another similar coil between the two lines at the local telephone central station opposite the railroad."
Brixton met us about eight o'clock that night in his now renovated den. Apparently, even the little change from uncertainty to certainty so far had had a tonic effect on him. I had, however, almost given up the illusion that it was possible for us to be even in the den without being watched by an unseen eye. It seemed to me that to one who could conceive of talking through an incandescent lamp seeing, even through steel and masonry, was not impossible.
Kennedy had brought with him a rectangular box of oak, in one of the large faces of which were two square holes. As he replaced the black camera-like box of the detectaphone with this oak box he