The form in which the sheets (of skin, parchment, bark, papyrus, or paper) were gathered, may have been rolls in which they were united to form a single page, or a square combination of successive leaves united only at one side. The former was of course the earlier mode, but the latter was also in use at a remote date. Greek and Roman scribes had evidently begun to prefer the square fashion during the early days of the Roman empire; and we may take it to have become the prevalent custom in the fourth century. Black ink has always been in use for writing, red and blue ink are of comparatively recent date. The use of gold ink, which was of course so costly that it could never be otherwise than rare, originated probably when the empire was as {4}yet unshaken by barbarian inroads; it was, however, not extinct in Rome during the sixth and seventh centuries, and was relatively not uncommon at the magnificent court of Byzantium. Late examples were produced in Gaul for the Frankish princes in the ninth century; and in these the simple splendour of the Roman style was embellished with ornamentation chiefly drawn from Irish and Anglo-Saxon models. Although people knew how to write and to read more than five thousand years ago, "a reading public," as we understand the term, came into existence for the first time in Greece in the fifth century B.C., and again in Rome in the first century B.C. By this it is meant that there were people who bought books for the pleasure of reading them, as distinguished from the class which produced or used books as an official necessity. The requirements of that reading public among the Greeks, led to the disuse of skins for the purpose of writing, since only a cheaper and more plentiful material could satisfy the demand. Egyptian papyrus being both cheap and plentiful, it was adopted and remained in use for over a thousand years among the people who spoke Greek and Latin. Books upon vellum or parchment--_charta pergamena_, an improved form of the old skins--were only produced occasionally, as luxuries, between the second century B.C. and the fifth century of our era. At this latter period, the reading public was extinguished in the revolutions of barbarian conquest, and the cheap material ceased to be necessary. In the absence of a popular demand for books, and when only persons of exceptional learning, churchmen, statesmen, and monks, experienced the need of reading and writing, the supply of vellum was sufficient, and this dearer material was relatively economical because of its durability. A reading public can hardly be said to have come into renewed existence till the fifteenth century, and then once more vellum was superseded by the cheaper material of paper. Paper, from linen or rags, had been made in the {5}Saracenic east for several centuries, but was little used in Europe till the thirteenth century, and was not fabricated in the west to any considerable extent until the fourteenth century.