ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



251 



Krusz's Epidiascope.*— This instrument is intended for the pro- 

 jection (1) of opaque objects in reflected light ; (2) of transparent 

 objects in transmitted light ; (3) of physical investigations in the hori- 

 zontal position with transmitted light ; (4) of microscopic objects with 

 the polarising Microscope ; 1(5) of i spectral, polarising, and interference 

 phenomena with the optical bench. The light-source is an arc-lamp 

 with a horizontal positive carbon and a vertical negative carbon. The 

 lamp is adjustable on runners. The light-rays emanating from the 

 crater B (fig. 57) are collected by the condenser K, and issue there- 

 from, according to the position ■ of the lamp, as a parallel, slightly 

 divergent, or convergent beam. The rays then pass through the 



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Pig. 57. 



cooling-trough W. Two mirrors, S a and S 4 , are placed under the 

 upper plate of the apparatus. When the projection of opaque objects 

 is required, as in fig. 57, the mirror S T is put out of action, and the 

 rays, after impinging on S 4 , are reflected on to the stage, which by means 

 of an inserted board now form an unbroken plane. The illuminated 

 object on the stage is focused through the objective 0, on to the ad- 

 jacent reversing-mirror S 5 , and thereby projected on to the screen. The 

 stage of the apparatus is large enough for the reception of drawings and 

 pictures with a breadth of 60 cm. and with any desired length. When 

 the apparatus is wanted for the projection of transparent objects, the 

 mirror S x is brought down into the position shown in fig. 58, so as to 

 receive the incident light, and the rays take the direction shown by the 

 dotted lines. After reflexion at S x the rays pass through an aperture 



* Deutsche Mechaniker-Zeitg. (Sept. 1908) pp. 166-8 (2 figs.). 



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