Length of Lines.—This leads to consideration of the effect length of lines has on reading.
The Board of Education of the city of New York disqualifies textbooks in which the length of line is more than 100 millimeters (about twenty-four picas, or four inches). The maximum length of line recommended by the British Association for the Advancement of Science in 1912 is about the same. Professor Huey, in “The Psychology and Pedagogy of Reading” (1907), says: “There is a general consensus in favor of the shorter as against the longer lines, with a tendency to favor 90 millimeters as a maximum, some placing the maximum at 100 millimeters.” Dr. Javal, the French oculist, who thirty-five years ago made tests in typography, believes the maximum should be considerably below 90 millimeters (about 21 picas).
It would be well, in order to arrive somewhere in determining the proper length of line, to consider the size and kind of type that makes up the line.
The author asks consideration of Examples [509] and [510]. The length of line is limited by authorities because the eye finds it difficult to read a long line of comparatively small type. Isn’t it true that healthy eyes can read a line of type twelve inches long set in fifty-four-point Caslon Oldstyle, say, with the same ease as a line four inches long set in eighteen-point Caslon Oldstyle?
By the same reasoning, the line of twelve-point Caslon Oldstyle set three inches wide (Example [509]) is as easily read, after the eyes are focused on it, as the line of eighteen-point Caslon set four inches wide.
The author suggests, then, that the proper length of type lines be ascertained by measuring one-and-a-half alphabets of the lower-case of the desired type, as is demonstrated in Example [510].
Let us try out the top group—Caslon Oldstyle. (This type-face seems smaller, according to body sizes, than Scotch Roman, for the reason that its descending strokes have not been cut off, while those of the Scotch Roman group have been shortened; but of this more later.)
A lower-case alphabet-and-a-half of twelve-point Caslon Oldstyle (with long descenders) measures 17½ picas in length, as will be seen in Example [510]. How it appears set in words in two lines of the same measure is to be seen in the upper part of Example [509]. According to the working out of the plan, 17½ picas is the ideal length of line for books using this twelve-point type. By referring back to Example [127] in the chapter on “Books,” the theory will be found borne out in practical use on a model book page.
Testing the length of lines by reading (Example [509]), it will be found, if the distance between the eyes and book is lengthened as the sizes grow larger, that the line is short enough not to necessitate a hunt for the beginning of the second line after the first is read.
The optical disadvantage of using in one piece of printing type-faces of any great contrast in sizes may be proved by focusing the eyes so as easily to read the eighteen-point size and then changing quickly to the eight-point size, attempting to read the latter without again focusing the eyes to fit the smaller type.