At these last words Theophrastus turned so pale that Signor Petito thought that he was going to faint. None the less he took the letter and the document, thanked Signor Petito, and went out of the flat. He walked straight out of the house and wandered about the streets for a long while. At last he found himself in Saint-Andrew-des-Arts Place; then he took his way to Suger Street, and opened the latch of an old-fashioned door. He found himself in a dark and dirty passage. A man came down it to meet him, and recognising him, greeted him. "How are you, Theophrastus? What good wind blows you here?" he said in affectionate tones. "How are you, Ambrose?" said Theophrastus gloomily. Since they had not met for two years, they had a hundred inquiries to make of one another. Ambrose was an engraver of visiting-cards by profession. He had been a printer in the Provinces; but having put all his capital into a new invention in printing, it had not been long before he found himself a bankrupt. He was a cousin of Marceline; and Theophrastus, who was a good soul, had come to his aid in the hour of his gravest trouble. Theophrastus sat down on a straw-seated chair in a little room which served as workshop, and was lighted by a large, dusty skylight in the ceiling. "You 're a scientific man, Ambrose," he said, still gloomily. "Nothing of the kind!" said Ambrose quickly. "Yes; you are. No one could teach you anything in the matter of paper." "Oh, yes: that's true enough. I do know paper." "You know all papers," said Theophrastus. "All," said Ambrose with modest pride. "If one showed you a piece of paper you could tell the age of it?" "Yes; I have published a monograph on the water-marks of the papers used in France during the seventeenth and eighteenth centuries. The Academy crowned it." "I know it. And I have the fullest confidence in your knowledge of papers," said Theophrastus with unrelieved gloom. "It's well-founded; but really it's a very simple matter. The oldest papers presented at first, when they were new, a smooth, glossy surface. But soon wire-marks appeared in them, crossed at regular intervals by perpendicular lines, both reproducing the impression of the metal trellis on which the paste was spread. In the fourteenth century they had the idea of utilising this reproduction by making it a mark of the source or mill which the paper came from. With this object in view, they embroidered in brass wire on the trellis mould, initials, words, and all kinds of emblems: these are the water-marks. Every water-marked sheet of paper carries in itself its birth-certificate; but the difficulty is to decipher it. It requires a little practice: the pot, the eagle, the bell..." Theophrastus opened his pocket-book and held out his scrap of paper with trembling fingers. "Could you tell me the exact age of this document?" he said. Ambrose put on his spectacles and held the paper up to the light.