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 Mi-
