Voigt &: Hochgesang. Gottingen. 137 



No. 2797. 



Voigt & Hochgesang, Gottingen. 



Principal: R. Brunnee. 



Makers of Cry stallographic- Optical Instruments. 



Microscopically thin sections of rocks. 



Minerals, Fossils etc. 



I. 



Microscope N. 1 A (Fig. 1) constructed according to suggestions of Prof. 

 C. Klein 1 ) for advanced mineralogical and petrographic research. 

 This instrument is fitted with the most recent and perfect apparatus for 

 all possible measurements in parallel polarized and convergent light. 

 The circle, which is made of a suitable alloy, is divided in half degrees. 

 The verniers read to single minutes. The circle is surmounted by a, 

 mechanical stage with scales and divided heads for reading and noting 

 its position. The polarizer is so arranged that quick changes may be 

 made from polarized to convergent light. 2 ) A second polarizer with very 

 large Nicol prism and highly refracting set of lenses and an objective 

 of numerical aperture 1.53 render the microscope available for measure- 

 ment of minerals of very low refractive power. The Bertrand lens 

 is fitted with rack and pinion. The optical equipment of the microscope 

 consists of the objectives Nos. 0, 1, 2, 4, 5, 7, 9, oculars Nos. 1 and 4 

 with micrometer, Nos. 2 and 3 with cross lines, Bertrand's ocular, 

 Oalderon's ocular, screw micrometer ocular, Babinet's compensator 

 ocular, one dark ground Nicol prism, one quartz wedge, selenite, quartz 

 and 1/4 undulation mica-plate. 



The above described Microscope is exhibited in the exhibition of 

 German Universities. 



In the Collective Exhibition, Group 21, the following instruments 

 and appliances are exhibited: 



Microscope No. i B. made according to the suggestions of 

 Prof. Klein, for mineralogical and petrographical research. 



The construction of this instrument is precisely the same as that 

 of No. 1A, excepting that it is not fitted with mechanical stage and 

 that the circle is divided in whole degrees only, the vernier admitting 

 of reading to Vio degrees. 



The instrument is supplied with objectives Nos. 1, 2, 4, 7, 9 and 

 oculars Nos. 2 and 3 with cross lines, Nos. 1 and 4 with micrometer, 

 screw micrometer ocular, quartz, mica and selenite plate. 



*) Vid. Nachrichten von der Ktfnigl. Gesellschaft der Wissenschaft zu 

 Go'ttingen 1884, No. 11, p. 434 etc. Neues Jahrbucli far Mineralogie, 1883, 

 I. Heft 2. Mikroscop. Physiogr. der petr. wichtig. Mineralien v. H. Rosenbusch 

 1887, I. p. 120; 1892. I. p. 126. 



2 ) Zeitschrift ftir Instrumentenkunde. 1891. April. 



