The writing was marked on the wax by means of a style in the same way that writing was formerly done in England on the curious sand tables. These styles are usually of iron, sometimes inlaid with brass, but they were also made of bronze, brass, wood or bone. They always have one end pointed to write with and the other flat to erase with. A space was often left in the thickness of the wooden edge of a diptych to keep the style in. The erasing in the case of the diptych was effected by rubbing the flat end of the style over it, and in the case of the sand writing-tablet by a plasterer’s level or a good shake. Sand tablets have been used up to quite recent times in elementary schools. But the sand writing was always temporary, whereas the wax writing is very lasting, one of those found at Pompeii bearing the date A.D. 55. It records a payment to Umbricia Januaria, and is the earliest Latin manuscript known. [Illustration: FIG. 13.--Roman diptych stylus.] Diptychs of similar form were widely used. They have been found in Egypt, and in England--remains of the Roman occupation--together with numbers of the styles used for writing with. Diptychs were kept together at the back by means of metal rings or thongs of leather, run through holes made in the wood, so that they are true prototypes of our modern books both as to form and manner of keeping together, the “stabbed” form of binding, that is to say, threads or bands or wires run through holes pierced along the back edge of the sections of a book, having been in continual use ever since rolls were first turned into books. When the diptychs were used as private letters they were further fastened with a tie or clasp in front, and this tie was often sealed with the sender’s signet in wax or clay. The Pompeian and all the other small wooden diptychs are unornamented, but at a later period, particularly from the second to the seventh century, Roman diptychs became of much importance and were often decoratively treated, being made of ivory and elaborately carved. Labarte, Gori, Westwood and Maskell have all written valuable works concerning these ornamental diptychs, and specimens of more or less excellence can be found in most museums that have any collection of carvings in ivory. The earlier examples are the best; later specimens rapidly decline in art value, although they are always of great historical interest. [Illustration: FIG. 14.--Byzantine diptych of ivory.] One leaf of one of the finest diptychs in existence is fortunately in the British Museum; it shows a full-length figure of an archangel with globe, cross and long-staff, and is supposed to have been made in the third or fourth century. A curious point about this leaf is its unusual size, about 16 by 6 inches, and it is said that such a piece could not be cut from any known elephant tusk. It is possibly mammoth ivory.