“Before we add any acid,” said he, “or introduce any fresh matter, we will adopt the simple preliminary measure of tasting the solution. The sugar is a disturbing factor, but some of the alkaloids and most mineral poisons excepting arsenic have a very characteristic taste.”

He dipped a glass rod in the warm solution and applied it gingerly to his tongue.

“Ha!” he exclaimed, as he carefully wiped his mouth with his handkerchief, “simple methods are often very valuable. There isn’t much doubt as to what is in that sugar. Let me recommend my learned brother to try the flavour. But be careful. A little of this will go a long way.”

He took a fresh rod from the rack, and, dipping it in the solution, handed it to me. I cautiously applied it to the tip of my tongue and was immediately aware of a peculiar tingling sensation accompanied by a feeling of numbness.

“Well,” said Thorndyke; “what is it?”