onJschool-books and eyesight. 235 



widespread efforts are being made to secure the fulfilment of the Com- 

 mittee's recommendations, at least so far as books for young children 

 are concerned. The Committee hopes that further progress will be 

 made in regard to books for boys and girls over fourteen years of age. A 

 diminution in the power of accommodation of the eye continues during 

 this period of life, whereas at the same age there is good educational 

 reason for an increased extent of reading and for the use of books 

 containing a considerable amount of information. Hence visual defects 

 frequently become evident at about the age of sixteen. The recom- 

 mendations in the Committee's typographical table issued in 1913 were 

 based on a balanced consideration, of the above facts, and it is important 

 that the standard proposed for readers o-\er twelve years should be 

 insisted upon. 



Investigations have been made during the last two years in order 

 to dbtain an objective measurement of the gloss of paper, and the 

 Committee is indebted to Mr. A. P. Trotter for designing a new form 

 of gloss-tester, and for carrying out tests with books and writing-papers 

 used in schools. 



The Committee observes : — 



(1) That glossiness of paper depends mainly on specular reflection, 



i.e., reflection as from polished metals; such reflection is apt to 

 interfere with binocular vision. The ideal surface for books 

 would exhibit no specular reflection ; all the reflected light 

 would be scattered or diffuse reflection, equal in all directions 

 and independent of thf direction of the incident beam. Such 

 absence of gloss is real sable in any fine white powder, such as 

 magnesia, but not in pi mting papers. No harm to eyesight is, 

 however, likely to accrue if the specular reflection is not exces- 

 sive ; hence the proportion of specular to diffuse reflection 

 affords a suitable index of the glossiness of paper. 



(2) That a large proportion of school-books and writing-papers are 



satisfactorily free from glare at angles of incidence not exceed- 

 ing 45 degrees. In most of these satisfactory books the 

 specular reflection does not exceed the diffuse reflection when 

 the hght is incident at 45 degrees, the paper being viewed from 

 the direction of the corresponding specularly reflected rays. 



(3) That when the specular reflection exceeds 56 per cent, (the 



diffuse reflection being then less than 44 per cent.), there is 

 likely to be injurious glare. The risk is greater if the book is 

 read in artificial light. 

 The Committee therefore hopes that publishers will select for school- 

 books papers from which the specular reflection at 45 degrees does not 

 exceed the diffuse reflection. Books in which the specular reflection 

 exceeds 56 per cent, of the total reflection (specular plus diffuse) must 

 be regarded as potentially injurious to eyesight. 



Writing-paper for school use should not give more than 54 per cent, 

 specular reflection at 45 degrees, since young writers often look 

 obliquely at the paper. 



The Committee finds that coloured maps can be produced without 

 extra expense or difficulty on paper conforming with the above rules. 



