— =" a SS eee 
ON THE INFLUENCE OF SCHOOL-BOOKS UPON EYESIGHT. 285 
the rest of the book. The same rules should be 
applied to test-cards. The use of hektographing 
or other multiplying processes is increasing in 
schools. Care should be taken to secure clear and 
legible copies. 
13. The Types for Mathematical Symbols, includ- 
ing those used for Algebra, should correspond 
with, or be larger than, the sizes of type recom- 
mended for the various ages. It is important that 
the smaller symbols should not be too fine. For 
children under twelve years no fractions should be 
employed less than 4 mm. in height of face; thus 
in 3 the distance from the top of the 3 to the 
bottom of the 4 should not be less than 4 mm. 
For pupils over twelve the minimum face height 
for fractions should be 35 mm. There should be 
a clear interval between the figures and the 
separating line. It should be easy to discriminate 
between the numerals 3, 6, 8 and 9. 
14. Squared Paper.—Use of squared paper 
should be restricted to work for which it is really 
required. If this be done, and paper with rulings 
not less than one-tenth inch apart be used, there 
will be little danger to vision. The use of milli- 
metre paper should be restricted to students over 
fourteen, and it should only be used by them ina 
good light—on exceptional occasions. 
15. Atlases—It does not appear possible to 
avoid some use in atlases of type which is below 
the desirable standard of size, and the care which 
should be exercised by teachers in regard to the 
children’s eyesight needs to be specially emphasised 
in this connection. Their use should be avoided 
when the illumination is below normal—the less they 
are used for home-work the better. Location by 
reference lines should be taught from the begin- 
