HALF PAY 



3788 



HALF-TONE 



Half Pay. Rate of pay issued 

 to officers of the navy and army 

 who have for some reason ceased 

 to do duty, and have been removed 

 from their corps, appointment or 

 command, but who are on the 

 active list and still eligible foi 

 employment. 



Half-timer. Name given to a 

 pupil who attends school for 

 approximately half the ordinary 

 hours, going to work in the others. 

 In England the Education Act oi 

 1870, and later Acts, made educa 

 tion compulsory, but local author! 

 ties were allowed to pass by-laws 

 permitting children to become halt- 

 timers on reaching a certain age, 

 generally 12 or 13, provided they 

 had reached a certain standard. 

 The number of half-timers in Eng- 

 land in 1911-12 was 70,255 r the 

 annual figures showing a steady 

 decrease in the number of these 

 partial exemption scholars. Most 

 were employed in textile factories 

 in Yorkshire and Lancashire. 



Attempts to end half-time were 

 resisted by employers and workers, 

 but the Education Act of 1918 

 provided for its abolition, and from 

 Jan. 1, 1921, local authorities had 

 no power to grant exemption from 

 attendance at school to an} 7 child 

 between the ages of 5 and 14. 

 Under the Employment of Women, 

 Young Persons, and Children Act 

 which came into force 1921, it was 

 illegal to employ any child under 

 14 in industry unless the child was 

 already so employed. See Children ; 

 Education ; Factory Acts. 



Half-tone. Photo-mechanical 

 process of making typographic 

 printing blocks from full-tone 

 originals such as photographs, 

 wash-drawings, and the like, as 

 distinguished from those in line. 

 While the making of line blocks by 

 photo-etching became commer- 

 cially practicable as early as 

 1 860-70, some years passed before 

 a satisfactory method was devised 

 for breaking up full-tone originals 

 into a form capable of printing 

 with type. In the earlier pro- 

 cesses of Pretsch, Dallas, and 

 Negre a gelatine relief was made 

 from a negative of the original. 

 This relief was rendered conductive 

 with black-lead and an electrotype 

 made from it. 



Other inventors broke up the 

 image by placing a ruled or 

 irregular screen in front of the 

 sensitive plate when photographing 

 the original with the object of re- 

 placing the continuous tone by a 

 fine pattern of dots or other form. 

 This is the method which is now 

 commercially used in making half- 

 tone blocks, but the present pro- 

 cess, which is purely optical and is 

 carried out with great rapidity and 



Half-tone. The same subject as reproduced through six different screens. 



(1), 150 lines per inch; (2), 135; (3), 120, the screen used for The Universal 



Encyclopedia blocks; (4), 100; (5), 80; (6), 64; 5 and 6 being commonly 



used for newspaper illustrations. See text 



facility, was evolved directly from 

 a mechanical and tedious method 

 independently worked out by 

 Pettit in France and F. E. Ives in 

 America in 1878. These ex- 

 perimenters, who were the first to 

 produce successful half-tone en- 

 gravings, made a plaster cast from 

 a gelatine relief of the original, the 

 high-lights forming the raised parts 

 and the shadows the hollows. The 

 cast was blackened on the sur- 

 face and ruled through, line by 

 line, with a V-shaped tool, the 

 action of the cutting V on the 

 black relief causing the high-lights 

 of the picture to be formed by fine 

 black lines where the white ground 

 of the plaster is most deeply cut ; 

 the shadows by fine white lines cut 

 away by the point of the V ; and in- 

 termediate tones by corresponding 



portions of white and black lines. 

 The excised relief was then photo- 

 graphed, a resist-image printed 

 from the negative on to metal, 

 and the latter etched. Ives per- 

 ceived that this translation of 

 the original into minute units of 

 black and white in correspondence 

 throughout with the tones froic 

 high-light to shadow, could be 

 very simply done by photographing 

 the original on to a sensitive plate 

 having a fine ruled screen of 

 crossing opaque lines placed at 

 the requisite distance close in 

 front of it. Cross-line screens for 

 this purpose were made by Levy 

 of Philadephia about 1880, and 

 from this time half-tones began 

 speedily to come into general use, 

 first for magazine and book illus- 

 tration, later in daily newspapers. 



