Writing seems also to have been common, at a very early period, on palm and olive leaves, and especially on the bark of trees--a material used even in the present time in some parts of Asia. The bark is generally cut into thin flat pieces, from nine to fifteen inches long and two to four inches wide, and written on with a sharp instrument. Indeed, the tree, whether in planks, bark, or leaves, seems in ancient times to have afforded the principal materials for writing on. Hence the word _codex_, originally signifying the "trunk or stem of a tree," now means a manuscript volume. _Tabula_, which properly means a "plank" or "board," now also signifies the plate of a book, and was so used by Addison, who calls his plates "tables." _Folium_ ("a leaf") has given us the word "folio"; and the word _liber_, originally meaning the "inner bark of a tree," was afterward used by the Romans to signify a book; whence we derive our words, "library," "librarian," etc. One more such etymology, the most interesting of all, is the Greek name for the bark of a tree, _biblos_, whence is derived the name of our sacred volume. Before I leave this stage of the subject, I will mention the way in which the Roman youth were taught writing. Quintilian tells us that they were made to write through perforated tablets, so as to draw the stylus through a kind of furrow; and we learn from Procopius that a similar contrivance was used by the emperor Justinian for signing his name. Such a tablet would now be called a stencil-plate, and is what to the present day is found the most rapid and convenient mode of marking goods, only that a brush is used instead of an iron pen or style. Writing and materials have so much to do with the invention of printing that I feel obliged to tarry a little longer at this preliminary stage. The most important of all the ancient materials for writing upon were papyrus, parchment, and vellum; and on these substances nearly all our most valuable manuscripts were written. Papyrus, or paper-rush, is a large fibrous plant which abounds in the marshes of Egypt, especially near the borders of the Nile. It was manufactured into a thick sort of paper at a very early period, Pliny says three centuries before the reign of Alexander the Great; and Cassiodorus, who lived in the sixth century, states that it then covered all the desks of the world. Indeed, it had become so essential to the Greeks and Romans that the occasional scarcity of it is recorded to have produced riots. Every man of rank and education kept _librarii_, or book-writers, in his house; and many _servi_, or slaves, were trained to this service, so that they were a numerous class.