204 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



object placed vertically. For this purpose the release of a catch enables 

 the dark chamber to be easily rotated until the projection lens occupies 

 a horizontal position ; the lamp-house is then rotated to the suitable 

 angle, and the effect is obtained by direct reflection from the opaque 

 object. This gives a great gain in brilliance. The illuminant recom- 

 mended is a hand-feed arc lamp for direct or alternating current, con- 

 nected by two feed wires to a switch attached to rear of base. 



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Fig. 16. 



Fig. 17 shows the apparatus fitted up so as to be available for 

 microscopic or for polariscopic (horizontal or vertical) projection. 



Spectroscopic projection is attained by adapting an adjustable slit 

 and an equilateral prism to the normal lantern. The slit narrows the 

 beam of light as much as desired before it passes through the projection 

 lens. The prism, placed in front of the projection lens, breaks up the 

 beam into its prismatic components before it is projected on to the 

 screen. 



Fig. 18 shows the balopticon fitted with Edison moving picture 

 (type B) attachment, the whole being mounted on a special table. The 

 attachment furnished has an automatic shutter and two film-reels in 

 fire-proof magazines. A lens is also supplied of suitable relative focus 

 to produce images from the films of the same size as those from the 

 slides or opaque objects. 



