In very early papers these rules cannot be safely followed, because early chain marks as well as early watermarks were not produced in the same reliable way. The paper being made in moulds with wire netting at the bottom, the impression came below the paper instead of above it as in the case of the roller, and also the sizes of the sheets were more likely to differ. Watermarks are the semi-transparent devices which show on certain pages of a printed book. They are to be seen on most papers of the fourteenth to the eighteenth centuries, and there has been a good deal written about them, especially abroad. The devices were outlined in wire and set in the bottom of the trough or on the wire roller I have just described, so that the lines are impressed upon the pulp just when it is in its most sensitive condition. The pressure from the wire device thins the pulp wherever it is touched, and so when dry the device shows lighter than the rest of the paper. These marks should be called wire marks rather than watermarks, and the French word for them, “Filigranes,” is more correct than ours. The difference in tint between a watermark and the rest of the paper is so distinct that a photographic negative placed under one will render a capital photograph of it, far better than any drawing, but it needs a long exposure. Watermarks are already of considerable value to Bibliographers, and it is likely that in the near future they will be much more noticed, especially in English books. Many frauds have already been detected by reason of the watermarks, as it is a point that _faussaires_ have so far paid little attention to. The marks are, however, not to be relied on after about 1750, as they do not run reliably in machine made or wove papers. Armorial devices have been largely used as watermarks. Many of the earlier marks show the arms of towns, especially continental ones, and among others there are the arms of France, Portugal, William and Mary and Queen Anne, shown in full heraldic outlines. [Illustration: FIG. 55.--English “hand” watermark, 1512.] The Holbein family of Ravensburg bore a bull’s head as their armorial badge, and they were paper makers, so the bull’s head shows on their paper as a watermark. It was afterwards much copied, and during the fifteenth and sixteenth centuries it became a favourite mark on German papers. There does not seem to have been any strict copyright in any of the devices used as watermarks. They were freely used by any one who cared to do so, but the copies were never very carefully made, they were always variants of the original. They were moreover generally accompanied by another mark, that of the maker, on another part of the paper. The same privilege of using a “maker’s” mark was also allowed to the silversmiths in addition to the official hall mark.