rammar in use in the middle ages, when
Latin was the foundation of all culture. It was, therefore, very
extensively used and it is supposed that more copies were printed of it
than of any other block book. It has the further distinction of being
the only block book printed on vellum. Ordinarily the desire for
cheapness and the much greater ease of handling the material caused the
block books to be printed on paper. The importance of the Donatus as a
book of reference and the hard usage it was likely to receive at the
hands of schoolboys caused the use of the more expensive but more
durable material.

Particular interest attaches to one block book called the Speculum
Humanae Salvationis or "Mirror of Salvation." In a way this book is the
connecting link between block books and type printed books. There is no
copy of this book in existence printed entirely from wooden blocks. Most
of the early editions are printed from movable types with a block
printed illustration at the head of each page. One of them, however, has
twenty pages of the text out of the sixty-two which constituted the
entire book printed from wood blocks. These twenty pages are inserted at
intervals among the others, and how and why they came there is a riddle
beyond guessing.

It has been conjectured by some that the long-held belief that Gutenberg
was a polisher of mirrors is erroneous and that the reference in certain
of the scanty documents concerning him to business about mirrors may
refer to attempts on his part to print an edition of this book, "The
Mirror of Salvation."

In making a block book the design was cut on the side of a flat piece of
wood, not on the end of the block as was the later practice in wood
engraving. Sometimes, as has been said, a design thus cut was only a
picture. Sometimes it was both picture and text. The design was cut in
relief, that is to say the wood was cut away leaving the design to be
impressed upon the paper raised. The block was then thoroughly wetted
with a thin, watery, pale brown material much resembling distemper. A
sheet of damp paper was laid on it and the back of the paper was
carefully rubbed with a dabber or burnisher. It is probable that other
inks were employed, especially for vellum, and it is also extremely
probable that a rude press, ancestor of the modern printing press, was
used to produce the impressions in many cases. The resulting book
consisted of sheets printed on one side only, although ther