160 



Projection Apparatus and Accessories. 



No. 50730 



50735. 1:10. 



Prices of Projection Apparatus. 



School Projection Apparatus, Model A, Figure 50,735, for projecting apparatus and photographs; 

 with Condenser, Achromatic Objective, Optical Bench, Change Frame with smaller frame inserted 

 for taking diapositives 9x10.5 cm, 8.5x10 cm and 9x12 cm; 1 stage and one movable slider 

 with stand in which to insert the change frame, the stage or other objects; on tall legs. 



Switchboards see page 169, Regulating Resistances for the apparatus with electric arc lamps - - see 

 pp. 1226 1228. Fixed Series Resistances, Transformers and flexible triple leads see pp. 168 and 169. Better 

 Optical and other Outfits see NOB. 50,750 50,767, p. 161. 



The housing is of black iron; it has a door, in the side wall, having dark glass peep holes, and a further 

 observation window on the opposite side. The lamp is manipulated from behind. For this purpose the back 

 is fitted with a sliding door which can be completely removed. The disturbing light radiated from behind is 

 prevented from issuing from the lantern by black curtains, the housing being well ventilated. The condenser 

 is fitted to the front wall, the optical bench being placed in front of the latter, and carrying two sliders: one 

 of those shown in the illustration carries the diapositive holder with change frame, while the other carries the 

 objective-holder together with the objective. 



As regards the various systems of lamps, the lantern of this apparatus is arranged so that all the lamps 

 included in the table of prices can be inserted e. g., instead of the hand-regulated lamp, a lamp with auto- 

 regulation, or a Nernst lamp or focus glow lamp, when the candle-power demands are not too great or if a 

 saving in current has to bo effected. Gas and spirit incandescent lamps will also fit the lanterns so that they can be 



Cl. 5427. 



