The most remarkable peculiarity in the presswork of the _Speculum_ is the embossed letters at the ends of the short lines.[163] They are most noticeable in the two Latin editions, which contain lines of unequal length. To the modern printer the purpose to be accomplished by the use of the old and worn types that produced these embossed letters is apparent at a glance. They served as bearers or guards to shield newer and better types in exposed positions from an impression which [p306] could not be regulated. This exposed position was at the ends of the long lines; the types that projected beyond their fellows received the hardest impression, and the printer knew no better method of shielding them than by the insertion of worn types at the ends of the shorter lines above and below.[164] This expedient was insufficient. On the margins of many copies of the _Speculum_ can be detected (for the grain of wood is unmistakable) the marks of impressions against wood. It seems that the pages of types were fastened in a mortised block of wood of the same height as the types. This block of wood not only served as a chase to hold the types, but as a bearer to shield the types from uneven impression. It steadied the descent of the platen, and diffused the impression equally over the entire surface. These bearers shielded the types from undue impression, but they made a new difficulty, for they were of the same height as the types. The inking of a form so constructed must have blackened with equal impartiality the types of the text, the worn types used as bearers, and the wooden chase. To lay a sheet of white paper over such a form would smear and blacken it at the ends of short lines and in the margins where no color was required. It became necessary to put a mask over these bearers, so that the ink on the bearers would not be transferred to the paper. This mask was substantially the same contrivance which modern printers call the frisket. It shielded the white sheet from contact with ink where ink was not required, but could not shield it from impression. It really strengthened and deepened the impression, producing the embossed letters in the short lines and the marks of wood in the margins. On [p307] some pages the slipping or displacement of this paper mask caused the false letters to be printed in black; on one other page the mask slipped so trivially that one-half of the false types was printed in black, while the other half was embossed in white; on another page the mask slipped over the text type, and obscured the end of the line. These were exceptional errors; the general execution of this part of the work shows that the printer was a man of some intelligence, and that with imperfect materials he performed a very difficult task. [Illustration: The Frisket, Tympan and Bed of a European Hand Printing Press. _A C_ The Frisket. _C B_ The Tympan. _B D_ The Bed.