196. Let the signs fº, 4º, 8º, etc., if used, represent the fold of the sheet as ascertained from the signature, not be guessed from the size.
In the older books this is important, and in modern books the distinction between the octavo and the duodecimo series is so easily ascertained that it is not worth while { 77} to be inaccurate. The size may be more exactly indicated, if it is thought worth while, by l. or sm., sq., obl., prefixed to the fold, as l. 8º, sm. 4º. The “vo” or “mo” should be represented by a superior º if it can be had, otherwise a degree-mark °, though manifestly improper, must be employed; it has abundant usage in its favor.
Another method of giving the form is fº (8), 4º (2), 8º (4), in which fº, 4º, 8º indicate the apparent form of the book as the terms folio, quarto, octavo are generally understood, and the figures within the parentheses show the number of leaves intervening between the successive signatures.
“In the folio the sheet of paper makes two leaves or four pages, in the 4º four leaves, in the 8º eight, in the 12º twelve, and so on. When a sheet of paper is folded into six leaves, making what ought to be a 6º book, it is called a 12º printed in half sheets, because such printing is always done with half-sized paper, or with half-sheets, so as to give a 12º size. From a very early period it has been universal to distinguish the sheets by different letters called signatures. At present a sheet has A on the first leaf or A1 on the first leaf and A2 on the second, which is enough for the folder’s purpose. But in former times the signatures were generally carried on through half the sheet, and sometimes through the whole. Again, in modern times, no sheet ever goes into and forms part of another; that is, no leaf of any one sheet ever lies between two leaves of another. But in the sixteenth century, and even later in Italy, it was common enough to print in quire-fashion, the same letter being used for the whole quire, and the leaves of the quire distinguished as they were successively placed inside of one another by the figures 2, 3, 4, so that a book actually printed in folio might have the signatures of a modern octavo. In exact bibliography such books are sometimes described as ‘folio in twos,’ ‘folio in fours.’ Rules are given for determining the form of printing by the water-lines of the paper and by the catchwords. It is supposed that the latter are always at the end of the sheet, and also that the water-lines are perpendicular in folio, octavo, and decimo-octavo books, horizontal in quarto and duodecimo. But in the first place a great many old books have catchwords at the bottom of every page, many have none at all; and as to the rule of water-lines, there are exceptions to every case of it.”[62]