ID A mee 
ON THE INFLUENCE OF SCHOOL-BOOKS UPON EYESIGHT. 283 
Approximate uniformity in length is desirable ; 
but not absolute uniformity. It is doubtful 
whether the power of fairly rapid intelligent reading 
can be attained without the unconscious Deciaaate 
ance of the swing from near the end of each line 
to near the beginning of the next. This swing 
may be compared with the motion of an oarsman’s 
body between the strokes. An occasional slight 
indentation in the lines helps the reader; but large 
ones, if frequent, hinder the acquisition of a good 
habit of swing. Children of eight years old should 
not have their reading confined to very short 
paragraphs, as the habit of swing has been found 
well established in good readers of between nine 
and eleven years of age. In other words, these 
readers made the necessary eye-movements with- 
out conscious effort and with great regularity. 
Unusual separation of letters should be 
avoided. For beginners, lines should not end in 
the middle of a word; the whole word should be 
carried to the next line and not be hyphened. 
The admission in the table of a four-inch line for 
the large type is a concession intended to meet the 
difficulty of securing an even set of the letters in a 
line of shorter measure. 
Good margins are restful to the eye, and are 
well worth their slight cost. Asa rule the margin 
at the top or ‘head’ of a page should be less than 
that at the bottom or ‘tail’; less on the inner 
side or ‘back’ than on the outer or ‘ fore-edge.’ 
So many influences, including optical illusions, 
have to be considered in determining the proportion 
of margin that it is not thought desirable to propose 
formule for the purpose. It should be considered 
a defect in a school-book if the width of fore-edge 
is less than half an inch, or of back-edge less than 
three-eighths of an inch, at any page of the book. 
