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 of such a letter would be careless. If he were in a hurry it opens up the interesting question why he should be in a hurry, since any letter posted up to early morning would reach Sir Henry before he would leave his hotel. Did the composer fear an interruption—and from whom?”

“We are coming now rather into the region of guess-work,” said Dr. Mortimer.

“Say, rather, into the region where we balance probabilities and choose the most likely. It is the scientific use of the imagination, but we have always some material basis on which to start our speculation. Now, you would call it a guess, no doubt, but I am almost certain that this address has been written in a hotel.”

“How in the world can you say that?”

“If you examine it carefully you will see that both the pen and the ink have given the writer trouble. The pen has spluttered twice in a single word, and has run dry three times in a short address, showing that there was very little ink in the bottle. Now,