Fig. 63.—4o.
—4o in size. If the once folded sheet be folded again across the other way we get a gathering with four leaves, or eight pages, called a quarto. The chain lines are horizontal, and the watermark in the middle of the back of pp. 4 and 5; there are two foldings and two tops of leaves to be cut.
—8o. If the quarto be again folded we get a gathering of eight leaves, or 16 pp., called an octavo, which is the commonest size for English books. In an octavo there are three foldings, the chain lines are perpendicular, the watermark is quartered at the tops of pp. 3, 4, 11 and 12, and there are two tops and two fronts to be cut.
The further foldings of 16o, 32o, and 64o are the same operations carried further, but although such sizes do exist they are so uncommon that a further description of them is not necessary.
—12o. In the case of a duodecimo a different initial folding is followed. The original sheet instead of being folded once across the middle, as in the case of a folio, is now folded into three equal divisions. The parallelogram thus formed is folded across its shorter diameter, and this again along its longer diameter. There is now a gathering of twelve leaves, or 24 pp., with four foldings, the chain marks perpendicular, the watermark halved at the tops of pp. 3 and 9, and there are two tops and four fronts to be cut. It is the commonest size of the smaller French books.
Fig. 64.—8o.
Fig. 65.—12o.