The proportions of large CAPITALS, shown above, are set by the Line-space (_footnote_, p. 221).
_The proportions of the margins to each other_ follow a sort of tradition (see fig. 70), the foot margin (4) usually being twice as wide as that at the top (2), the side margins generally greater than the top and less than the foot. The two pages of an _opening_ may be viewed as one sheet having two columns of text; and the two inner margins, which combine to form an interspace, are therefore made narrow (about 1-1/2 each), so that together they are about equal to one side margin (fig. 70). These proportions (1-1/2: 2: 3: 4) approximate to the proportions common in early MSS.
Sufficient and proportional margins add greatly to the usefulness and beauty of a book. That the writers and illuminators used them when books were read and valued in a way we can scarcely realise now, shows that such things are not, as some might suppose, a matter of affectation. Besides the natural fitness of the common proportions commends them: a deep foot margin is a foundation to the whole, and gives a spare piece for the reader to hold,[20] and wide side margins rest the eyes and keep the text from "_running off the page_" at the end of each line; and (the _two_) narrow inner margins combine to separate the pages sufficiently, but not too far, so that they form two "columns" together, _framed_ by the outer margins of the open book.
When books are meant to be bound, from 1/16 inch to 1/8 inch extra margin should be allowed _all round_ the page for the cutting down and binding. The [p107] binding is apt to encroach on the inner margins, especially in vellum books, which do not open fully; in order, therefore, that the inner margins may keep their proper width, an extra width of 1/8 to 1/4 inch (according to the stiffness of the material) is allowed.
The shape, size, and margins of the page (already settled) together determine the length of the _writing-line_ (see fig. 71); and the _size of the writing_ should be such as will allow a reasonable number of words to that line.[21]
Eight or nine words to the line is a common proportion in ordinary printed books, and may be taken by the scribe as his ordinary _maximum_. Lines having very many words are difficult to read.