“Yes,” I said, “I can follow each of your arguments. I confess, however, that I am unable to understand how you arrive at the double visit to the optician.”

Holmes took the glasses in his hand.

“You will perceive,” he said, “that the clips are lined with tiny bands of cork to soften the pressure upon the nose. One of these is discoloured and worn to some slight extent, but the other is new. Evidently one has fallen off and been replaced. I should judge that the older of them has not been there more than a few months. They exactly correspond, so I gather that the lady went back to the same establishment for the second.”

“By George, it’s marvellous!” cried Hopkins, in an ecstasy of admiration. “To think that I had all that evidence in my hand and never knew it! I had intended, however, to go the round of the London opticians.”

“Of course you would. Meanwhile, have you anything more to tell us about the case?”