Visible and Invisible

Mr. Tilly had only the briefest moment for reflection, when, as he slipped and fell on the greasy wood pavement at Hyde Park Corner, which he was crossing at a smart trot, he saw the huge traction-engine with its grooved ponderous wheels towering high above him. "Oh, dear! oh, dear!" he said petulantly, "it will certainly crush me quite flat, and I shan't be able to be at Mrs. Cumberbatch's séance...