35 



3. "Illuminating Apparatus, No. 41, Fig. 14, being a double-lens con- 

 denser of 1,0 numerical aperture and 6,7 mm focal length. 



A small iris-diaphragm is centrally fixed to the mount of the condenser. 

 This diaphragm, being an indispensable adjunct to this form of illuminator, is in- 

 variably supplied with it. 



Price: Marks 22. . Code-word: Parali/ar. 



Fig. 14. 

 Illuminating Apparatus, No. 41. 



A. Side and sectional elevation. B. Plan-view of the iris-diaphragm. 

 (Full Size.) 



When subsequently ordering the illuminating apparatus., 

 No. 4-1, separately, the cylinder -diaphragm, belonging to the stand 

 should be sent to us. 



When in using Stands IV b , VI and VII obliqiie light is required, the con- 

 densers and sliding sleeves must be removed; the azimuth and obliquity of the 

 light-pencil may then be varied within a fairly wide margin by appropriate manipu- 

 lation of the mirror, which is movable in all directions. 



With Stands IX a and X a , as also with the Dissecting Stands, illumination by 

 transmitted light only can be effected by the mirror or, when diffuse light is 

 required, by means of white paper disks. 



II, Illumination by reflected light, 



In the examination of opaque objects, metal specimens, &c. , an 

 appliance for adequately lighting up the specimens from above is indispensable. 

 If the free working distance of the objective used is very large, it generally 

 answers sufficiently well to illuminate the object by the direct rays of daylight or 



., Sena, 



