From very early ages, leather was more or less used as writing material, but in the 2nd century B.C., owing, it is said, to the scarcity and high price of papyrus, Eumenes II, King of Pergamus, a city of Asia Minor, invented or caused to be invented, a writing material made of dressed skins. These skins were not tanned but were dressed by another method which left them flexible but gave them a smooth hard surface which could be easily written on. This material was called, from the name of the city, _pergamena_, from which we get our "parchment." This term is now practically reserved for sheepskins which are harder than other skins used for the purpose. Parchment was long used for legal documents and is still used for college diplomas and other similar purposes. The general term, however, for this type of writing material, which was made from a variety of skins, is vellum. Vellum, of course, came in sheets, and while a single sheet might be rolled as diplomas are to this day rolled for delivery, it was ordinarily used in the sheet form and played an important part in the development of the book. In the manufacture of vellum the skins of a variety of the smaller animals were used. For example, the famous Alexandrian codex, one of the oldest known copies of the Bible, is written on antelope skin. The skin was first carefully cleaned and the hair removed by soaking in a solution of lye. It was then thoroughly scraped with a knife to remove all fatty or soft parts. It was then rubbed down with pumice stone. Finally it was polished with agate. Paper is said to have been invented by the Chinese at an unknown but very early date. It was introduced to Europe by the Arabs about the 10th century A.D. It was made of linen or rags and did not vary greatly from the rag paper of to-day. As the process of manufacture is fully described in the book on paper (No. 13) of this series, description is not necessary here. Paper was not much used in Europe until the invention of printing. Being much less substantial than vellum it did not commend itself for the making of manuscript books. Paper was, however, immediately found to be much better suited to printing than any other material, and with the advent of the printed book it very quickly drove other writing materials out of common use. Owing to its having some resemblance to papyrus it was given the old name, the word paper being derived from papyrus.