Dr. Priestley, although he was known by name to a very large circle of newspaper readers, who were periodically entertained by one or other of his thrusts at some pet nostrum of the moment, such as the craze for brown bread or the discovery of vitamines, rarely or never appeared in public. He had even escaped the doubtful honour of having his photograph reproduced in the evening papers, though this perhaps was a disadvantage, since it would certainly have been unrecognizable. He was therefore in no sense a public figure, in that he was most unlikely to be distinguished from the ordinary crowd of travelling humanity. He sat in the train without any attempt at disguise, studying an ordnance map which he had laid open upon his knees.