I. DISTRIBUTORS. 177 



The lamp is automatic, the carbon poles being drawn asunder in proportion 

 to the strength of the battery power used ; this is effected by drawing iron 

 rods into a hollow coil of insulated copper wire. The lantern has two nozzles, 

 one intended for exhibiting screen experiments in spectrum analysis, polari- 

 sation, refraction, reflection, diffraction, &c. The second nozzle is for ex- 

 hibiting diagrams on the same screen, without altering the arrangement of 

 the apparatus for physical experiments. 



818. Lithographs for the Stereoscope, from drawings 

 by J. Miiller, Hessemer, Oppel, Nell. 



J. Wilhelm Albert, Frankfort- on- Maine. 



The coloured drawing marked with A (upon grey cardboard) is the 

 original made by the late Prof. Miiller. Images 2, 3, and 4 serve for a 

 stereoscope without glass. The other images refer to stereometrical, astro- 

 nomical, and optical (colour combinations) subjects. Some images appear, 

 by a slight change of position, in low or high relief. 



819. Edelmann's Spectral Lamp, for the projection of 

 the spectra. M. Ph. Edelmann, Munich. 



820. Printed Treatise to the same. 



M. Ph. Edelmann, Munich. 



821. Duboscq's Lantern. To be used in connexion with 

 the following apparatus : 



1. Top with illuminating lens ; is to be employed with spectral 

 slit and polariscope. 



2. Spectral slit ; can be regulated by means of a fine screw. 



3. Stand with convex lens ; serves for the projection of the 

 rays in spectrum experiments. 



4. Two hollow prisms. 



5. A prism plate for two prisms, arranged for being turned and 

 put higher or lower. 



6. Stand with holder for a prism ; can be regulated. 



7. Polariscope. 



8. Lens system, with four-inch illuminating lenses and achro- 

 matic objective ; serves for the projection of photographic and 

 other glass images of about 3 inches in diameter. 



9. Microscope. This can be screwed to the end of the preceding 

 system of lenses, after the objective has been removed. 



10. Regulator for producing electric light ; can be regulated. 



11. Hydro-oxygen gas lamp. 



12. Apparatus for hydro-oxygen illumination, arranged for the 

 projection of opaque objects. 



A. Kriiss, Hamburg. 



82 la. Photogenic Lantern. M. J. Duboscq, Paris. 



822. Double demonstrating Oxy-hydrogen Lantern, 

 with triple condensers, consisting of two 10-inch plano-convex 



39508. M 



