about
midnight
Then they began short walks back and forth , but soon both sat down on the ground , with their rifles between their knees , and after that they did not stir . Watching as closely as he could Dick could not observe the slightest movement on the part of either , and he knew that they were asleep . He laughed to himself , pleased , in a way , to know that he had been right , although it was only another evidence of the carelessness and indifference general throughout the train . He fell asleep himself in another half hour , but he awoke about midnight , and he was conscious at once that he had been awakened not by a troubled mind , but by something external and unusual . He was lying with his right ear to the ground , and it seemed to him that a slight trembling motion ran through the solid earth . He did not so much hear it as feel it , and tried to persuade himself that it was mere fancy , but failed . He sat up , and he no longer observed the trembling , but when he put his ear to the ground again it was stronger .