"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 of the evidence furnished. Even the
very dilute solution which I have been able to make of the
material scraped from these spots gives characteristic absorption
bands between the D and E lines, as they are called.
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