This need of a fundamental balance has its basis in its pleasure-giving value. I have adverted to the analogy between book-design and architecture, let me point now to an equally pertinent analogy with the structure of poetry. "Verse," says Poe, "originates in the human enjoyment of equality, fitness. To this enjoyment, also, all the moods of verse--rhythm, meter, stanza, rhyme, alliteration, the refrain, and other analogous effects--are to be referred." Specifically, the parts of a book--half-titles, headings, etc., etc.--should be, severally _and collectively_, related as are such structural elements in verse as recurrent rhythms, rhymes, and refrains.
We must now consider the decorated or illustrated book. In the first place, it should be understood that no form of decoration or illustration is legitimate in the strictly fine book except such as are printed from wood or metal engraved by hand, preferably in relief which comports with type both in physical character and in the means by which the image is imparted to the paper. Process-engravings are disqualified not only because of the preponderant mechanical factor, but because mechanical engraving in relief cannot produce a line of the delicacy and purity obtained with the engraving tool. As a corollary to the principle of integration set forth above let us take first the type of decorated book to which most obviously it applies. A book carrying on various pages head-bands of varying depth and varying tone--deep, shallow, black and heavy, light and delicate--will produce a disturbing effect. Less obvious but hardly less disturbing is a succession of initial letters differing in size, in tone, or in position on the page. The book with initial letters strewn through the text, sometimes several on a single page, is a challenge to the designer. When thus arbitrarily employed it is important, in order that the initials shall not be obtrusive, that they be so selected as to size (in proportion to the page) and so integrated with the book as a whole that their "accidental" character is either disguised or lost and their recurrence actually contributes to the unity of the volume by virtue of their consistent accentual value.