We must ever bear it in mind, however, while considering the large number of books treasured in the Alexandrian Library, or in any other ancient collection, that a manuscript roll--the common form of most ancient books--was generally written on one side of the parchment or papyrus only and therefore could contain at most only one-half the amount of matter embraced within a book of leaves and pages. We have already called attention (p. 62) to the change in literature from the roll book to the book of leaves; and would now note the further change in the roll-book by which the smaller rolls, convenient for handling, were substituted for the enormous and cumbrous ones often encountered. The bulkier manuscript rolls, composed as they were of parchment or papyrus,--chiefly of papyrus at Alexandria--sometimes having the length of one hundred and twenty feet or even longer, came to be divided into smaller rolls as making up a given large work,--the number of which being determined by the size of the respective works, or, somewhat, as in poetry, by the character of the composition. The object of this was to facilitate handling and reference, and, incidentally, the preservation of the manuscript;--the opening portions of the roll, as also the initial pages of a book of leaves, being most frequently handled, were subjected to greatest "wear and tear." Under this change, the History of Herodotus, e. g., was multiplied into nine and the Iliad of Homer into twenty-four "books" or volumes; and the entire Bible which, if contained in one roll would prove unwieldly and almost incapable of use, would require thirty or forty or more rolls. The size of the Medieval Bibles, when made up in a book with leaves instead of the roll form, was immense. They were veritable libraries in themselves--consisting of four or five, in one instance of fourteen, great folio volumes. The Bible, however, being written by many different authors and having a great diversity of themes, would, by reason of this difference in authorship and subject-matter, more readily lend itself to an arrangement into separate rolls or books than many of the early classic writings. Indeed, the Bible, while it is THE BOOK, is, essentially, a large collection of separate books. Not the Bible alone but other large works, as the Iliad and the Odyssey, notwithstanding the unity and continuity of their themes, were also divided into "books" or rolls, and these were numbered or named by the letters of the Greek alphabet:--"Iliad A" would designate the first book of Homer's Iliad, and so on unto the end of the composition. This change to smaller books, and thus to a larger number of separate volumes, came about or was facilitated and expedited in the Library at Alexandria. One, Callimachus, the grammarian, seems to have been greatly instrumental in its furtherance; for, as says Mr. Putnam, "From his time the cumbrous scrolls began to disappear, and as well for the