But during many ages the article most in use, and of which the consumption was so great as to form a principal branch of the commerce of the Mediterranean, was that manufactured from the papyrus of Egypt. Many manuscripts written upon this kind of paper in the sixth, and some even so early as the fourth century, are still extant. It formed the material of by far the larger proportion of all books from very early times till about the seventh or eighth century, when it gradually gave place to a still more convenient manufacture. The papyrus, or Egyptian reed, grew in vast quantities in the stagnant pools formed by the inundations of the Nile. The plant consists of a single stem, rising sometimes to the height of ten cubits; this stem, gradually tapering from the root, supports a spreading tuft at its summit. The substance of the stem is fibrous, and the pith contains a sweet juice. Every part of this plant was put to some use by the Egyptians. The harder and lower part they formed into cups and other utensils; the upper part into staves, or the ribs of boats; the sweet pith was a common article of food; while the fibrous part of the stem was manufactured into cloth, sails for ships, ropes, strings, shoes, baskets, wicks for lamps, and, especially, into paper. For this purpose the fibrous coats of the plant were peeled off, the whole length of the stem. One layer of fibres was then laid across another upon a block, and being moistened, the glutinous juice of the plant formed a cement, sufficiently strong to give coherence to the fibres; when greater solidity was required, a size made from bread or glue was employed. The two films being thus connected, were pressed, dried in the sun, beaten with a broad mallet, and then polished with a shell. This texture was cut into various sizes, according to the use for which it was intended, varying from thirteen to four fingers' breadth, and of proportionate length. By progressive improvements, especially in the hands of the Roman artists, this Egyptian paper was brought to a high degree of perfection. In later ages it was manufactured of considerable thickness, perfect whiteness, and an entire continuity and smoothness of surface. It was, however, at the best, so friable that when durability was required the copyists inserted a page of parchment between every five or six pages of the papyrus. Thus the firmness of the one substance defended the brittleness of the other; and great numbers of books so constituted have resisted the accidents and decays of twelve centuries.