“And it is because of this that you let us find you?” asked Bertram.
“I had a curiosity to know who had so strangely traced my actions.”
“But what was the poison?” asked Professor Gehren.
“I think Mr. Jones has more than a suspicion,” replied the doomed man, with a smile. “You will find useful references on yonder shelf, Mr. Jones.”
Moving across to the shelf, Average Jones took down a heavy volume and ran quickly over the leaves.
“Ah!” he said presently, and not noticing, in his absorption, that the host had crossed again to the tiroir and was quietly searching in a compartment, he read aloud:
“Little is known of cyanide of cacodyl, in its action the swiftest and most deadly of existing poisons. In the ’40’s, Bunsen, the German chemist, combined oxide of cacodyl with cyanogen, a radical of prussic acid, producing cyanide of cacodyl, or diniethyl arsine cyanide. As both of its components are of the deadliest description, it is extremely dangerous to make. It can be made only in the open air, and not without the most extreme precaution known to science. Mr. Lacelles Scott, of England, nearly lost his life experimenting with it in 1904. A small fraction of a grain gives off vapor sufficient to kill a human being instantly.”
“Had you known about this stuff, Average?” asked Bertram.
“No, I’d never beard of it. But from its action and from the lettered cabinet, I judged that—”
“This is all very well,” broke in Mr. Assistant Secretary Thomas Colvin McIntyre, “but I want this man arrested. How can we know that he isn’t shamming and may not escape us, after all?”