Once settled in the train, the Professor breathed more freely. Most of his fellow-passengers had stayed on the ship, which was carrying them on to swarm over a succession of other places as he had just left them swarming over Marseilles. The train he got into was not very crowded, and should other travellers enter the compartment, his ear-pads would secure him from interruption. At last he could revert to the absorbing thought of the book he was planning; could plunge into it like a diver into the ocean. He drew a deep breath and plunged.... Certainly the compartment had been empty when the train left Marseilles—he was sure of that; but he seemed to remember now that a man had got in at a later station, though he couldn’t have said where or when; for once he began to think, time vanished from him as utterly as space. He became conscious of the intruding presence only from the smell of tobacco gradually insinuating itself into his nostrils. Very gradually; for when the Professor had withdrawn into his inner stronghold of Pure Reason, and pulled up the ladder, it was not easy for any appeal to reach him through the channel of the senses. Not that these were defective in him. Far from it: he could smell and see, taste and hear, with any man alive; but for many years past he had refrained from exercising these faculties except in so far as they conduced to the maintenance of life and security. He would have preferred that the world should contain nothing to see, nothing to smell, nothing to hear; and by negativing persistently every superfluous hint of his visual, auditive or olfactory organs he had sheathed himself in a general impenetrability of which the ear-pads were merely a restricted symbol. His noticing the whiff of tobacco was an accident, a symptom of his still disorganized state; he put the smell resolutely from him, registered “A Man Opposite,” and plunged again into the Abstract. Once—about an hour later, he fancied—the train stopped with a jerk which flung him abruptly out of his corner. His mental balance was disturbed, and for one irritating instant his gaze unwillingly rested on silver groves, purple promontories and a blue sea. “Ugh—_scenery_!” he muttered; and with a renewed effort of the will he dropped his mental curtain between that inconsequent jumble of phenomena and the absolutely featureless area in which the pure intellect thrones. The incident had brought back the smell of his neighbour’s cigarette; but the Professor sternly excluded that also, and the train moved on....