pression of his teeth, almost before he realised what Kennedy was doing. The precedent set, so to speak, Kennedy approached Doctor Forden. He demurred, but finally consented. Mrs. Phelps followed, then the nurse, and even Shaughnessy.
With a quick glance at each impression, Kennedy laid them aside to harden.
"I am ready to begin," he remarked at length, turning to a peculiar looking instrument, something like three telescopes pointing at a centre in which was a series of glass prisms.
"These five senses of ours are pretty dull detectives sometimes," Kennedy began. "But I find that when we are able to call in outside aid we usually find that there are no more mysteries."
He placed something in a test-tube in line before one of the barrels of the telescopes, near a brilliant electric light.
"What do you see, Walter?" he asked, indicating an eyepiece.
I looked. "A series of lines," I replied. "What is it?"
"That," he explained, "is a spectroscope, and those are the lines of the absorption spectrum. Each of those lines, by its presence, denotes a different substance. Now, on the pavement of the Phelps mausoleum I found, you will recall, some roundish spots. I have made a very diluted solution of them which is placed in this tube.
"The applicability of the spectroscope to the differentiation of various substances is too well known to need explanation. Its value lies in the exact nature
