The name _librarius_ was given not only to the booksellers, but also to slave librarians, and to scribes, the latter being sometimes distinguished by the name _scriptores librarii_. _Librarii antiquarii_ were writers who were specially skilled in copying ancient manuscripts. The word _scriba_ commonly denotes a _secretary_ rather than what we should now call a _scribe_.
In Athens a class of booksellers, [Greek: bibliographoi], appears to have existed as early as the fifth century B.C.; see Poll. VII. 211. The name [Greek: bibliopôlai] was subsequently used, and adopted by the Romans.
THE TECHNIQUE OF ANCIENT MANUSCRIPTS[15].
_Parchment._ With regard to the preparation of parchment and other kinds of skin for writing on (_Pergamena_ and _Membrana_) there is little to be said. The skins of many different animals have been used for this purpose both in classical and mediaeval times, especially skins of calves, sheep, goats and pigs. Unlike manuscripts on papyrus, parchment or vellum[16] manuscripts were usually covered with writing on both sides, since the ink does not show through from one side to the other, as it is liable to do on the more absorbent and spongy papyrus paper. For this reason complete or partial erasures were much easier to execute on vellum than on papyrus. The writing was first sponged so as to remove the surface ink, and the traces that still remained were got rid of by rubbing the surface of the vellum with pumice stone. In some cases the manuscript was erased from the whole of a vellum codex or roll, and the cleaned surface then used to receive fresh writing.
_Palimpsests_; manuscripts of this class, on twice-used vellum, were called _palimpsests_ ([Greek: palimpsêstos]); see Cic. _Fam._ vii. 18. Several important texts, such as the legal work of Gaius, have been recovered by laboriously deciphering the not wholly obliterated writing on these palimpsests. During the early mediaeval period, when classical learning was little valued, many a dull treatise of the schoolmen or other theological work of small interest was written over the obliterated text of some much earlier and more valuable classical author.
In some cases it appears that papyrus manuscripts were made into palimpsests, but probably not very often, as it would be difficult to erase the ink on a roll of papyrus without seriously injuring the surface of the paper.