So much for Type. The printer possesses also Spaces and Leads as a normal part of his typographical material, straight lines of metal known as rules, braces, and finally a more or less indiscriminate collection of ornaments--head and tailpieces, flowers, decorated initial letters, vignettes and flourishes. Another decorative medium at his option lies in his command of colour; red is, with sound instinct, the most frequently used. For emphasis, heavy faces are used. White space is an important item of composing-room equipment--margins, blanks, etc., being filled in with what are known as "quotations." The selecting and arranging of these elements is known as Composition. Imposition is the placing of the composed matter upon the sheet. Printing includes impressing in due order, perfecting the sheet in due register (backing up), regulating the inking, and achieving a crisp type-page. Finally the tone, weight and texture of the paper are important factors entering into the completed result.
Typography, therefore, controls the composition, imposition, impression and paper. Of paper, it is at least necessary to demand that it be capable of expressing the value of the composition; of imposition, that the margins be proportionate to the area of the text, affording decent space for thumbs and fingers at the side and bottom of the page. The old-style margins are handsome in themselves and agreeable to the purpose of a certain kind of book, but are obviously not convenient in books where the page dimension is unavoidably small or narrow, or the purpose of the book is to be carried in the pocket. For these and other kinds of book, the type may be centred on the measure of the page, and slightly raised above ocular centre.
Imposition is the most important element in typography--for no page, however well composed in detail, can be admired if the _mise-en-page_ is careless or ill-considered. In practical printing today, these details of imposition are on the whole adequately cared for; so that it is possible to report that the mass of books presents a tolerable appearance. Even a badly composed work may give a good appearance if it is well imposed--good imposition redeeming bad composition, while a good composition would be effectively ruined by bad imposition.