Megadiascope. 1203 



Kohl's Megadiascope. 



General. 



The employment of electric light has greatly facilitated the introduction of various forms of 

 projectors for educational purposes. The convenience, cleanliness and high candle-power of projection 

 apparatus saving an arc lamp as the source of illumination are such valuable qualities, that the use 

 of such apparatus cannot be too highly recommended. 



The high candle power especially enables experiments to be carried out which are 

 impossible, or, at least, the same amount of completeness is not possible, when other sources of light 

 are utilised. In connection with the complete range of experiments mention may be made of p o 1 a- 

 r i s a t i o n and spectrum experiments, the projection of microscopical 

 p r e p a r a t i o n s, and, more especially, the projection by reflected light of 

 drawings, book, etc., illustrations and opaque objects. 



For demonstration purposes the projection apparatus must be so built as to be adaptable to 

 all the exigencies of demonstrating, and these are very numerous. 



With a view to obtaining the maximum degree of adaptability we have constructed a new pro- 

 jection apparatus, in two sizes, to which we have given the name "Megadiascope". This apparatus 

 can be thoroughly recommended for the following purposes: 



a) Employing transmitted Light. 



1. Projection of d i a p o s i t i v e s (F i g. 4) ; 



2. Projection of apparatus which are erected on the optical bench of the 



megadiascope (Fig. 5) ; 

 jf 3. Projection of apparatus independently of the optical bench, the instru- 



ments being placed in front of the megadiascope; 



4. Projection of apparatus lying horizontally (magnets with lines of force, 

 o fluid strata, etc.) by transmitted light (Fig. 6); 



? 5. Projection of microscopical preparations by means of the projection 



microscope with or without ocular (Fig. 7 and 7 a) ; 



6. Projection of microscopical preparations with a stand microscope 



(Fig. 8); 



7. Projection of stable, flowing and liquid crystals and their observation 



during existence, by means of the projection microscope fitted with heating and cooling 

 device: Fig. 11 (special descriptive catalogue on application); 



8. Demonstration of Spectrum phenomena (Figs. 12) ; 



9. Demonstration of Polarisation phenomena in parallel and convergent light 



(Fig. 13 to 19); 



10. Demonstration of Interference and Diffraction phenomena (Fig. 20 



to 22); 



11. Projection in n a t-u r a 1 tints with Ives' trichrome apparatus (Fig. 23); 



12. Projection in natural tints by diffraction (Fig. 24); 



13. Projection with the cinematograph (Fig. 25). 



b) Employing reflected Light. 



14. Projection of Wood-Cuts, Drawings and Flat Objects (F i g. 26) ; 



15. Producing a small pencil of light for the Lissajou curves, the 



oscillograph, etc. 



In conjunction with the wide scope of adaptability, the new megadiascope is 

 very simple and convenient to manipulate and the apparatus can be changed over from one mode of 

 projection to another in a few moments by turning one or two handles. 



Source of Light. The source of light is a direct current arc lamp with horizontal carbons, 

 the crater of the positive carbon being turned towards a parabolic mirror. The total quantity 

 of light from the lamp is reflected by the concave mirror on to the condenser, while in the case of pro- 

 jection apparatus having carbons arranged vertically or obliquely only a comparatively small portion 

 of the total light passes into the condenser. By adopting this advantageous arrangement, considerable 



