ON THE INFLUENCE OF SCHOOL-BOOKS UPON EYESIGHT. 277 
vision. Pure white paper gives the greatest con- 
trast with the ink, and therefore a paper which is 
white or slightly toned towards cream-colour is to 
be preferred under average conditions of class-room 
illumination. A hard-wearing paper of suitable 
quality should be used, as a soft paper has two 
defects—(1) it is readily soiled, (2) the surface is 
easily rubbed off and the detritus is injurious. 
The surface should be fairly smooth, because a 
rough-surfaced paper necessitates a heavy im- 
pression in order that the unbroken surface of 
each letter may appear, which impression is liable 
to cause a still rougher surface on the other side 
of the sheet. The print of one side must not 
show through from the other, and the printing 
must not affect the evenness of the surface of the 
other side. These rules also apply to illustrations, 
which afford a good test of the opacity of the 
paper. Books are occasionally bound and pressed 
before the ink is dried, and a faint impression of 
the opposite sheets causes a haze. Copies with 
this defect should be rejected. 
3a. Mode of binding books—Books should be 
stitched with thread. Books should open flat and 
should not require the restraint of the hand to keep 
them so; stabbing or clipping should therefore 
be avoided. If not flat, the convex surface of 
the page gives rise to eye-strain. On recent tests 
of a large number of school-books Mr. Bishop 
Harman reports that certain small books with very 
good paper and type could not be passed as 
satisfactory because they were clipped from side to 
side with wire staples. The books could not be 
opened flat ; the back margin was lost and some- 
times even the print nearthe back. The excessive 
handling needed to keep such books open would 
soon cause the pages to be soiled. Even in the 
