STEREOSCOPE 



5549 



STEREOTYPING 



The Screen. The screen should have a plain 

 white surface perfectly flat and free from wrin- 

 kles. Lecture rooms are usually fitted with a 

 white wall for a screen. Heavy muslin hemmed 

 and bound with cord, so that it can be tightly 

 stretched, makes a very satisfactory screen, and 

 screens of this sort are in general use. 



The Slides. The pictures generally used in 

 stereopticons are photographs on glass and are 

 known as slides. The American slide is 4x3^4 

 inches, the English slide 3*4 inches square. 

 They may or may not be colored by hand. 

 Since the perfection of colored photography, 

 beautiful slides are made by that process (see 

 PHOTOGRAPHY, subhead Color Photography). 

 Because the lens inverts the picture the slide 

 must be inverted in the lantern to have it ap- 

 pear erect upon the screen. 



Dissolving Views. The dissolving view effect 

 is produced by a double 1 lantern with the ob- 

 jectives so adjusted that each covers the same 

 field on the screen, and by an attachment which 

 gradually shuts off the light from one picture 

 as it is turned on the other. In the hands of 

 a skilful operator very pleasing effects are pro- 

 duced. W.F.R. 



Consult Gage's Optic Projection; Norton's The 

 Lantern and How to Use It; Tennant's Coloring 

 Lantern Slides. 



.STEREOSCOPE, ster' e oskohp, an instru- 

 ment through whose lenses photographs are 

 transformed into pictures that are quite life- 

 like, with an effect of depth and distance and 

 solidity ordinarily possessed only by actual 

 scenes and objects. The first stereoscope was 

 invented in 1838 by Sir Charles Wheatstone in 

 England, but the instrument which came into 

 common use was an improved and simplified 

 model which was developed by Sir David Brew- 

 ster. Oliver Wendell Holmes, in the United 

 States, brought out still another model, based 

 on the same principle as Brewster's machine 

 but much changed in appearance. 



The principle of the stereoscope is compara- 

 tively simple. It must be remembered that 

 the eyes of a human being may be compared 

 to cameras; each eye reproduces a separate 

 picture, and the brain combines them into one. 

 Because the eyes are some distance apart, the 

 pictures reproduced are not exactly alike. Each 

 eye sees more of one side of a given object 

 than does the other; together, the two eyes see' 

 farther around the sides of an object than can 

 one eye alone. This is what gives objects the 

 effect of standing out from their backgrounds. 

 In a stereoscope the eyes see, through lenses, 



two separate photographs, exactly alike, but 

 differing to just the degree that the actual 

 scenes would have differed when seen by the 

 eye. These two photographs, which are placed 

 in a rack and arranged so that each eye sees 

 only one, are combined by the brain into one 

 picture, which gives the lifelike effect. 



In taking stereoscopic pictures, one camera 

 with two lenses is commonly used, although 

 two separate cameras would, of course, serve 

 the same purpose. Theoretically, the lenses 

 should be placed exactly as far apart as are 

 the human eyes, but in practice it is found 

 more satisfactory to increase the distance, 

 thereby securing an effect of greater depth and 

 distance. 



Not many years ago nearly every family 

 possessed a stereoscope, and it occupied with 

 its pictures a prominent place on the parlor 

 table. The popularity of the device has de- 

 creased with the advent of moving pictures and 

 of books with halftone illustrations. A.C. 



STEREOTYPING, ster'e o type ing. A stereo- 

 type is a plate made of type metal and used 

 in printing. The process of making such a 

 plate is known as stereotyping. The type is 

 set and locked into forms. The face of the 

 type is then brushed over with a brush con- 

 taining a small quantity of oil. A pulp con- 

 sisting of a mixture of clay and papier-mache 

 is then pressed down on the forms so that a 

 perfect impression of the face of each type is 

 made in the pulp. Next, the form is placed in 

 a chamber and baked until the pulp is dry and 

 hard, when it is taken from the type. This 

 mold, or matrix, as it is called, is then ready 

 for the stereotype plate, which is made by plac- 

 ing the matrix in a box face up and pouring 

 melted type metal over it. This hardens at 

 once, forming a solid plate of type metal, and 

 from this the page is printed. Plaster of Paris 

 or clay may be used for the matrix, but papier- 

 mache is in general use. 



Plates for use on small presses are flat, but 

 those used on the rotary presses on which daily 

 papers are printed are in the form of a half cyl- 

 inder (see PRINTING PRESS). Stereotype plates 

 are inexpensive and can be quickly made, the 

 time required being about fifteen minutes. 

 They are specially adapted to newspaper work. 

 A number of plates can be made from the 

 same matrix, and in all large cities there are 

 firms that make a specialty of supplying coun- 

 try newspapers with a part of their subject 

 matter in this way (see NEWSPAPER). The 

 use of the stereotype is now limited to printing 



