HALFTONE 



2666 



HALIBUT 



graphs and the like. Halftones are extensively 

 used in the illustration of books, magazines 

 and newspapers. A zinc etching (which see) 

 will reproduce solid masses of black or white, 

 and will show separate lines, but it will not 

 show gradations of tone; in a zinc etching 

 everything is either black or white. A half- 

 tone takes its name from the fact that it does 

 actually show the middle or half tones of a 

 picture. This is accomplished by means of a 

 glass screen, which causes the essential differ- 

 ence between a halftone and any other form 

 of photo-engraving. 



If a halftone is examined with a magnifying 

 glass it will be seen to be a mass of tiny dots, 

 which are caused by the screen. A piece of 

 the finest sheet glass is covered with a varnish 

 of wax and asphalt, and is then ruled diag- 

 onally with minute lines; the number of lines 

 may be as many as 300 to the inch, but is 

 usually not over 150 or 200. The greater the 

 number of lines the finer will be the resulting 

 halftone. The ruling is done by an automatic 

 machine carrying a diamond-pointed graver, or 

 cutter. The plate is treated with hydrofluoric 

 acid, which eats or bites into the lines where the 

 graver has scraped away the varnish. The 

 lines are later filled with an opaque coloring 

 matter which is hardened in the plate by bak- 

 ing in an oven. Another plate similarly pre- 

 pared is then cemented to the first plate in 

 such a way that the lines on one are at right 

 angles to the lines on the other. The two 

 plates thus form a screen, in which the trans- 

 parent parts are separated by tiny dots and 

 occupy about one-third of the entire surface. 



A photograph of the picture or object to be 

 reproduced is taken through the ruled screen, 

 which is placed at a proper distance in front 

 of a sensitive plate. When the plate has been 

 exposed the result is a photographic negative, 

 composed of rows of small dots at regular 

 intervals. The dots are uniform in size, but 

 vary in blackness or intensity with the rela- 

 tive high lights and shadows of the original. 

 After the negative is developed a print from 

 it is made on a copper plate, which has been 

 specially prepared with a coating of fish glue, 

 albumin, water and bichromate of ammonia. 

 Where the dots on the photographic negative 

 allow light to pass through, this mixture will 

 harden, and the rest of the coating is then 

 washed off in water. The plate is etched in an 

 acid bath, but the acid affects only those parts 

 which are protected by the hardened fish glue 

 and albumin. 



The etching of a halftone requires great 

 skill, and several bitings are usually necessary 

 before the plate shows the proper gradations 

 of tone. An indefinite number of electroplates 

 (see ELECTROPLATING) can be made from the 

 original halftone. The halftone or the electro- 

 plates can be placed on a press, either with 

 or without type matter. A halftone requires 

 a very smooth (highly finished) paper for good 

 results. W.F.Z. 



HALIBURTON, hoi' i bur tun, THOMAS 

 CHANDLER (1796-1865), a Canadian humorist 

 and jurist, best known by his pen name, SAM 

 SLICK. Haliburton was born at Windsor, N. S., 

 and attended King's College in his native 

 town. He was 

 called to the bar 

 in 1820, was ap- 

 pointed chief jus- 

 tice of the Infe- 

 rior Court of 

 for the Middle 

 Common Pleas 

 Division of Nova 

 Scotia in 1829, 

 and in 1841 be- 

 came a judge of 

 the provincial 

 supreme court. THOMAS C. HALIBURTON 

 After serving with distinction on the supreme 

 bench for fifteen years he resigned and re- 

 moved to England, where he was from 1859 

 until a few months before his death a Con- 

 servative member of the House of Commons. 



Despite his brilliant career as a jurist it is 

 as a humorist and satirist, under the above pen 

 name, that he is best remembered. The Sam 

 Slick sketches, which first appeared in a local 

 paper, pictured a Yankee clockmaker, whose 

 shrewd sayings and knowledge of' human 

 nature won immediate recognition. These 

 sketches were collected and published in 1837 

 under the title of The Clockmaker, or Sayings 

 and Doings oj Samuel Slick of Slickville. A 

 second series of Slick stories appeared in 1838, 

 and a third in 1840. Judge Haliburton also 

 wrote The Old Judge; The Letter Bag of the 

 Great Western; Traits of American Humor; 

 and An Historical and Statistical Account of 

 Nova Scotia. G.H.L. 



HAL'IBUT, one of the largest and most 

 prized of the family of flatfishes, the name be- 

 ing derived from the word holy, since long 

 ago it was extensively used for food upon holy 

 days. It is a member of the flounder family 

 and is characterized, as are other flatfishes, by 



