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.
"There's a date," he said. "172… The