acid on the crystals. There was not a change in them.

Quickly he reached up into the rack and took down a bottle labeled
"Potassium Bichromate."

"Let us see what an oxidizing agent will do," he remarked.

As he gently added the bichromate, there came a most marvelous,
kaleidoscopic change. From being almost colorless, the crystals
turned instantly to a deep blue, then rapidly to purple, lilac,
red, and then the red slowly faded away and they became colorless
again.

"What is it?" I asked, fascinated. "Lead?"

"N-no," he replied, the lines of his forehead deepening. "No. This
is sulphate of strychnine."

"Sulphate of strychnine?" I repeated in astonishment.

"Yes," he reiterated slowly. "I might have suspected that from the
convulsions, particularly when Josephson said that the noise and
excitement of the arrival of the ambulance brought on the fatal
paroxysm. That is symptomatic. But I didn't fully realize it until
I got up here and tasted the stuff. Then I suspected, for that
taste is characteristic. Even one part diluted seventy thousand
times gives that decided bitter taste."

"That's all very well," I remarked, recalling the intense
bitterness yet on my tongue. "But how do you suppose it was