Page:Popular Science Monthly Volume 70.djvu/551

Rh should be a rationalization of these printed letter-forms that have come down to us in such a happy-go-lucky fashion, and it is to be hoped that either the Carnegie Institution or some department of research in a well-equipped university may take hold of the matter and see that the work is thoroughly done.

Among further printing requirements that are important and that should be insisted on, the letters should have sharp clear-cut outlines, and should be deep black. The paper should be pure white, but without gloss, the latter being especially trying to the eyes. According to Cohn and Sack the paper should have a minimum thickness of.075 millimeter. Paper of a slightly yellowish tinge is probably not injurious and is preferred by Javal. But in general the legibility depends on the contrast between the black of the printed forms and the white of their back-ground, and colored or gray papers lessen this difference and thus diminish legibility. Pure white light gives the greatest legibility. The print of one side must not show through from the other, and the printing must be so done that it will not affect the evenness of surface of the other side.

It is important that wall charts and maps should not contain more names than are absolutely necessary for purposes of instruction, and that these should be in large clear type; or the most important names for reference at a distance and by classes may be in the large type, with the others in type fulfilling the requirements for school-books and for use by individuals at the ordinary reading distance from the chart or map. Burgerstein and Netolitzky advise that school maps should not present the physical and political features on the same map, in the interest of greater legibility. Names printed on colored map surfaces need to be in larger rather than in smaller type than that used in books, if legibility is to be maintained, as any other back-ground than white means diminished legibility.

The writing upon slates is considerably less legible than that upon good white paper. In the case of blackboards the surface is apt to be gray after erasing, and this, of course, lessens the legibility very considerably. It is important that the blackboard surface be deep black, without gloss from reflection so far as this is possible; and that it be kept clean, avoiding the gray effect. Teachers and pupils should acquire the habit of writing on the blackboard in a large plain hand, as the greater distance at which the writing is read and the usually diminished legibility makes this of importance, and especially in the primary school grades.

In stating the requirements above, I have had in mind the needs of adult readers and of the older school children. The younger children must have a type much larger than the minima there stated. The reading of young children has not been sufficiently studied to