700 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



tho case of opaque, and transmitted light with transparent (or at least 

 translucent) objects. As compared with Zeiss' projection apparatus with 

 an optical bench (Catalogue, No. 249) it possesses the following charac- 

 teristic advantages: — (1) Greater latitude in the shape and size of 

 objects ; (2) when reflected light is used, the illumination is more per- 

 fect ; (3) transition from operation with reflected to transmitted light 

 is effected with greater speed and convenience ; (4) the apparatus is 

 easily adjusted for projection obliquely upwards ; (5) the several com- 



Fig. 131. 



ponent parts are better protected against dust and improper usage. On 

 the other hand, owing to the absence of the optical bench, the epidia- 

 scope lacks somewhat the manysidedness of application so characteristic 

 of Zeiss' other projection apparatus. The epidiascope is about 4 ft. 11 in. 

 in length, 2 ft. 6 in. in width, and about 4 ft. 11 in. high. The height 

 is so calculated that a person standing on the floor at the side of the 

 apparatus may be able to work it with ease and comfort. The source 

 of light used is a search-light lamp adjusted for a current of 30 or 50 

 amperes. The objective supplied cannot be exchanged for one of differ- 



