Prepared skins of animals have been the most generally used of all materials for covering bindings of manuscripts or printed books. Leather is tanned skin, and the hair is generally removed. Bindings that have the hair still left on the leather are usually of an elementary kind and are intended to be carried about in pockets. They are not common. Vellum (calf skin), and parchment (sheep skin), are not tanned, but are prepared with lime and are white. Not uncommonly, especially in Germany, other skins were so prepared. Pig skin, deer skin, goat skin, horse skin, and donkey skin were all “vellumised,” and are all very strong and take excellent impressions in blind. It is likely enough that vellum was used for the first covering of books, simply enclosing the sections, the ends of the bands drawn in, without boards. Such bindings are excellent for thin books, and they were successfully re-introduced in recent times by William Morris, always used with ties, as otherwise the vellum crinkles up. “Vellum” bindings made now, unless specially ordered, are only ordinary bindings in boards covered with vellum. Vellum is strong, but has some disadvantages. Although gold looks beautiful upon vellum it is difficult to work, and title labels do not stick to it well. If kept near the light it turns to something very like egg-shell and chips off. This defect was known to librarians in past times, and they met it by keeping their vellum books backs inwards, the forages outwards. Many instances of this manner of keeping vellum books occur in the Bodleian Library at Oxford, and they generally have their old pressmarks, and sometimes titles, written across the top of the forage. Old vellum was cut thick, and seldom ornamented, and if kept dry in the dark it is an excellent material. The same peculiarities exist in the case of parchment, which is, however, a very inferior skin, thinner, weaker, and not so good looking. Parchment is frequently described, and used, as vellum, and few purchasers know the difference; but the market value of parchment is less than half that of vellum. Vellum is particularly well suited for bindings kept in large towns, as dust does not stick to it, and it is easily cleaned. In time it assumes a creamy colour that is delightful. From the late sixteenth century until now, vellum stained green has been commonly used in England.