Probably the first use was as plain smooth boards only; examples of such are still in existence. Then of boards thinly covered with, usually, black wax. A pair of such tablets, wax-covered, was a common form of a Roman pocket-or memorandum-book. It was also used as a means of conveying messages, the reply being returned on the same tablets. The method was to write on the wax with a fine-pointed instrument called a style, the reverse end of which was flattened. When the person to whom the message was sent had read it, he (or she) simply flattened out the writing, smoothed it level, and then wrote the reply on the same wax. School-children did their exercises on these tablets, housewives and stewards kept their accounts on them, and on them literary people jotted down their ideas as they do now in their pocket-books. Extant examples of these early books, or tablets, are fairly numerous, and may be seen in most public museums. A codex of two leaves was called a diptych; of three, a triptych, etc. The codex form was used for legal documents, wills, conveyances, and general correspondence. Hence the Roman postman was called a _tabellarius_, the tablets containing correspondence being tied with a thread or ribbon and sealed. This custom of sending letters on tablets survived for some centuries after Augustan times. Wattenbach gives several interesting instances of their mediæval use.[6] [6] _Schriftwesen_, 48. Of course when the tablet gave place to the codex of skin or paper, the papyrus was too brittle and fragile for practical utility, and examples, as we have seen, were very rare; but vellum soon became popular. We may mention, in passing, that the papyrus roll gave us a word still in use in diplomatics, the word _protocol_. The first sheet of a papyrus roll was called the πρωτόκολλον. It usually contained the name of place and date of manufacture of the papyrus, and was stamped or marked with the name of the government officer who had charge of the department. In the vellum codex, though each leaf might have only one fold, and thus technically be considered as a folio, the actual shape of it was nearly square, hence its name of _codex quadratus_. When other forms of books, such as octavo, duo-decimo, etc., came into use, it was in consequence of the increased number of foldings. The gatherings, originally quaternions or quires, became different, and those who undertake to examine MSS. with respect to their completeness have to be familiar with the various methods.[7] This kind of knowledge, however, though useful, is by no means essential to the story of illumination. [7] Wattenbach, _Schriftwesen_; Madan, _Books in Manuscript_, _etc_. CHAPTER IV GREEK AND ROMAN ILLUMINATION The first miniature painter--The Vatican Vergils--Methods of painting--Origin of Christian art--The Vienna Genesis--The Dioscorides--The Byzantine Revival.