THEOPHRASTUS says that the papyrus books of the ancients were no other than rolls prepared in the following manner: Two leaves of the rush were plastered together, usually with the mud of the Nile, in such a fashion that the fibres of one leaf should cross the fibres of the other at right angles; the ends of each being then cut off, a square leaf was obtained, equally capable of resisting fracture when pulled or taken hold of in any direction. In this form the papyri were exported in great quantities. In order to form these single leaves into the "scapi," or rolls of the ancients, about twenty were glued together end to end. The writing was then executed in parallel columns a few inches wide, running transversely to the length of the scroll. To each end of the scrolls were attached round staves similar to those we use for maps. To these staves, strings, known as "umbilici," were attached, to the ends of which bullae or weights were fixed. The books when rolled up, were bound up with these umbilici, and were generally kept in cylindrical boxes or capsae, a term from which the Mediaeval "capsula," or book-cover was derived. "The mode in which the students held the rolls in order to read from them is well shown in a painting in the house of a surgeon at Pompeii. One of the staves, with the papyrus rolled round it, was held in each hand, at a distance apart equal to the width of one or more of the transverse columns of writing. As soon as the eye was carried down to the bottom of a column, one hand rolled up and the other unrolled sufficient of the papyrus to bring a fresh column opposite to the reader's eye, and so on until the whole was wound round one of the staves, when, of course, the student had arrived at the end of his book." Eumenes, king of Pergamus, being unable to procure the Egyptian papyrus, through the jealousy of one of the Ptolemies, who occupied himself in forming a rival library to the one which subsequently became so celebrated at Pergamus, introduced the use of Parchment properly "dressed" for taking ink and pigments and hence the derivation of the word "pergamena" as applied to parchment or vellum, the former substance being the prepared skin of sheep, and the latter of calves. The sheets of parchment were joined end to end, as the sheets of papyrus had been, and when written upon, on one side only, and in narrow columns across the breadth of the scroll, were rolled up around staves and bound with strings, to which seals of wax were occasionally attached, in place of the more common leaden bullae.