描述
Dr Martin wore a close-fitting black silk cap. Why? Well, the answer to the old riddle, "Why does a miller wear a white hat?" is, "To keep his head warm." That answer would do for a reply to the question why this grey, anxious-looking Dr Martin wore a close-fitting black silk cap as he sat poring over an old book opposite Phil Carleton, who also bent over a book; but he was not reading, for he had a pencil in his fingers and a sheet of paper covering one page, upon which sheet he was making notes.