618 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Martens Ball-jointed Metallographic Preparation Microscope.* 

 This instrument is shown in fig. 96, and is intended to be used for 

 observing the progress of the polishing and etching operations required 

 to adapt specimens for metallography. As is evident from the figure, 

 the stand here takes the form of a double ball- jointed arm. By this 

 means the specimen can be viewed at any angle. In order to avoid any 



Fig. 96. 



risk of injury to high-priced objectives and oculars, which might arise 

 from the proximity of the etching and polishing substances, a special 

 series of achromatic objectives and Huyghenian oculars is supplied by 

 Messrs. Carl Zeiss.f 



Voigtlander and Sons' Large Mechanical Stage.|— This is desig- 

 nated No. 1 by the makers. Its character will be understood from 



* C. Zeiss' Catalogue, entitled "Estimate for an Outfit for the Photomicro- 

 graphy of Metals," Jena, March 1907; and Martens and Heyn, " Ueber die 

 Mikrophotographie im auf!allenden Licht uud liber die mikrophotographischen 

 Einrichtungen der Konigtech. Versuchanstalt in Charlottenburg (Mitt. Konig- 

 technik Versuchanstalt, Berlin, 1899, p. 85). f Tom. cit., p. 5 



t Catalogue (English Edition) 1907, p. 17. 



