It is a delicate and essential matter to fix upon the length of the type page, and a difficult question to fix the margins. There is a mass of literature bearing upon these matters, but they cannot in every case be decided according to arbitrary rules. It is usually safe to be guided by the usual rules in proportioning a page of type, and in placing the page upon the paper. A thorough understanding of the principles of art as they may be applied to printing will suggest occasional infractions of mechanical rules in the interests of good art. Exactly what is to be the procedure in every instance cannot be formulated into rules, but it is always possible to explain justifiable infractions of rules by reference to principles of art. When it is found impossible to thus justify departures from rule, precedent or convention, it is evident that art would have gained if the rules had been adhered to.

The treatment of the format of a book has become somewhat of a moot question, though it is evident that the advocates of the strictly conventional method are gradually drawing practical printers into agreement with them, and that their opponents rely upon the spirit of philistinism for their chief justification, confining their arguments largely to contradiction unfortified by either logic or precedent. Philistinism is not entirely evil, but the present is not a time of such slavish conformity as to clothe it with the appearance of a virtue. Protest is the instinctive spirit of today. In printing there is too much of it. We need more conformity, if conformity be interpreted not to mean blind adherence to precedent but a large and active faith in the saving virtue of demonstrable principles.

Proportion, balance, in a limited sense composition as understood in art, and optics must be considered in adjusting the format of a book. The size and shape of the book must determine the exact dimensions of the page and the margins. The leaf of the ordinary book which is generally approved is fifty per cent longer than it is wide. This proportion is often varied, and for different reasons, but it may be accepted as a standard.

The margins of a correctly printed book are not equal. The back margin is the narrowest, the top a little wider than the back, the front still wider, and the bottom, or tail margin, the widest of all. Why this scheme for margins has grown to be authoritative, and adopted by good bookmakers, is not entirely clear. Nearly all the literature upon the subject is devoted to attempts to justify the custom instead of explaining its origin. The best justification that can now be offered is the evident fact that the custom is agreeable to publishers, to authors, and to discriminating readers.

It is often alleged that there is some law of optics that is in agreement with the custom, but it might be difficult to establish such a claim though it is not necessary to attempt to refute it. We are accustomed to this arrangement of the margins in the best books, and that to which we have become accustomed requires no defense, scarcely an explanation. It is certain that the format of a book appeals to us as right only where this arrangement of unequal margins is strictly observed. It is easy to imagine that our eyes rest more contentedly upon the pair of pages before them when those pages incline toward the top of the leaves and toward each other. The eye of the bookish person is undeniably better satisfied if the margins are proportioned as specified. There may be grounds for doubting the claim that the reasons for such satisfaction are optical; there are some plausible arguments to support such a contention. It is a question for oculists.

The other reasons for the evolution of the book format into its present form are logical. If they do not lead to the conclusion that art has been served and justified in full they assuredly do not lead to a contrary conclusion. The early paper makers produced a sheet that was uneven in shape and variable in size, and the pressman was compelled to make large allowance on the front and tail margins. The back and top margins could be reckoned, as when the sheet was folded by the print they would be uniform. The front and tail margins were made wide enough to allow for the unevenness of the paper and for the trim. It was inevitable that the allowance should be too great, and that to preserve the proper form and proportion for the book the front and tail margins should occasionally be left wider than the back and head margins. This, it may be imagined, did much to fix the present custom. The ancient handmade papers were thicker on the fore edge of the sheet than in the center, and as the bookbinder could not beat the edges flat they had to be trimmed off.

In the old days books were taken more seriously than they now are, and studious readers desired to annotate their copies of favorite books. The front and tail margins were used for this purpose, and they were therefore given their larger proportion of the sheet. In the fifteenth century this motive for wide margins was recognized by all printers, and many of them went so far as to provide printed annotations for all four of the margins.

There were other motives for fixing the margins as we have them. Whether the optical and the artistic motives, purely as such, may explain the modern format more logically than the historical motives do, may be debatable. The question is not vitally important. We wish to see the format of our books made as the best practice makes it, whether our taste is inherited as a habit or is acquired through our artistic cultivation.

Accepting therefore the dictum as it stands, without pressing an inquiry as to its authority or its legitimacy, it remains something of a problem to fix the margins and place the page of a book. When all suggestions and rules are considered it will be found that it is not often that the ordinary book page will submit gracefully to variation of the rule that the length be determined by cutting the page into two triangles, the hypotenuse of either of which shall be twice the width of the page. The page-heading should be included in this measurement, but if the folio is placed at the foot, either in bare figures or enclosed within brackets, it need not be included. This formula must often be disregarded, especially when the book is not to be proportioned in conventional dimensions. No other form is as satisfactory however, and it is quite within the bounds of the practice of the better bookmakers to consider it as the approved conventional page. Whenever it is varied the guide must be a general sense of appropriateness, having consideration for all the other varied elements.

There are other rules. One that was much in vogue at one time, and is esteemed now by some good printers, makes the type page one-half more in length than its width. This rule is restricted in its application. It will not do for a quarto page, nor for a broad octavo. Another rule provides that the sum of the square inches on the back and top margins shall be one-half the sum of the square inches on the front and tail margins. This is difficult to apply in practice, for obvious reasons, except as a test to determine the correctness of margins already fixed.

The margins must be adjusted with the intent to make the two pages lying exposed to view properly harmonize with the book leaf, and adjust themselves to the tyrannical optical demands of the eyes of the reader. This requires a very strict and careful adherence to rules well understood by good printers, as well as a courageous disregard of those rules when the exigencies of the case demand it. There are many other things to consider. The general character and purpose of the book must be taken into account, the size of type, and whether it is to be leaded or set solid, the quality and weight of paper, etc. A bible, guide book, or directory, need not have wide margins, nor a book printed on small type and thin paper; and a book the type for which is not leaded should be given less margin than is allowed for a page of leaded type. While the same general scheme for margins is applicable to nearly all good books, of whatever shape and size, when the contents and object do not dominate the physical character, it is obvious that the dimensions cannot in all cases be fixed according to the same formulas. A quarto page must have wider margins than an octavo, but they must bear a like relative proportion to each other. A quarto page must be proportioned differently than an octavo; it must be shorter by about one-seventh.

The width of the margins must in some degree depend upon the amount of white in the page of type, upon the tone of the type page. This involves the character of the type face quite as much as the spacing and leading given it, as some type faces have such light lines as to give the page a very light tone, even when the type is set solid and the spacing is close, other types have such heavy lines as to demand wide spacing, leading, and wide margins, to bring the tone down to a proper degree of grayness.

Consideration of all these questions affecting the format, and especially the margins, of a proposed book lead to the conclusion that it is good practice to select the paper as the first step in the planning of a book that is intended to be made upon artistic lines, and upon this foundation to build the typography and the binding, according to the rules of harmony and of proportion.