noon
In one place he found tiny tracks , as though a small bird had run quickly across it , and had stamped the imprint of its feet on the hard surface . It was Paul 's first lesson in geology , and it gave him his first idea that this hard slate , and the veins of coal enclosed between its solid walls , might have had a previous existence in another form . He pondered upon the length of time that must have passed since those ferns grew , and since that running bird made those footprints , and finally concluded to ask Derrick if he knew . At noon , after Harry Mule had been sent jingling to his stable , Derrick rejoined his friend , and they ate lunch together . As they talked of the strange markings on the walls , and Derrick confessed that he knew no more concerning their age than Paul , the latter suddenly paused , and with a slight gesture directed attention to something in the roadway . Looking in the direction indicated , Derrick saw , sitting bolt-upright on its hind-legs , and gazing steadily at them , an immense rat . He was quite gray , and evidently very old ; nor did he seem to be in the least bit afraid of them .