He suddenly had a surprise; at the most unexpected moment, and without ceasing to walk in a straight line, he perceived that he was no longer ascending; the water of the gutter plashed against his heels instead of coming to his toes. The sewer was now descending; why? Was he about to reach the Seine suddenly? That danger was great, but the peril of turning back was greater still, and he continued to advance. He was not proceeding toward the Seine; the shelving ridge which the soil of Paris makes on the right bank empties one of its water-sheds into the Seine and the other into the Great Sewer. The crest of this ridge, which determines the division of the waters, designs a most capricious line; the highest point is in the Sainte Avoye sewer, beyond the Rue Michel-le-comte, in the Louvre sewer, near the boulevards, and in the Montmartre drain, near the markets. This highest point Jean Valjean had reached, and he was proceeding toward the engirdling sewer, or in the right direction, but he knew it not. Each time that he reached a branch he felt the corners, and if he found the opening narrower than the passage in which he was he did not enter, but continued his march, correctly judging that any narrower way must end in a blind alley, and could only take him from his object, that is to say, an outlet. He thus avoided the fourfold snare laid for him in the darkness by the four labyrinths which we have enumerated. At a certain moment he recognized that he was getting from under that part of Paris petrified by the riot, where the barricades had suppressed circulation, and returning under living and normal Paris. He suddenly heard above his head a sound like thunder, distant but continuous; it was the rolling of vehicles. He had been walking about half an hour, at least that was the calculation he made, and had not thought of resting; he had merely changed the hand which held Marius up. The darkness was more profound than ever, but this darkness reassured him. All at once he saw his shadow before him; it stood out upon a faint and almost indistinct redness, which vaguely impurpled the roadway at his feet and the vault above his head, and glided along the greasy walls of the passage. Stupefied, he turned around. Behind him, in the part of the passage he had come from, at a distance which appeared immense, shone a sort of horrible star, obliterating the dark density, which seemed to be looking at him. It was the gloomy police star rising in the sewer. Behind this star there moved confusedly nine or ten black, upright, indistinct, and terrible forms. CHAPTER II. EXPLANATION.