Improved Metallurgical Microscope. By Walter Roseuhain. 147 



been met by applying a rack-and-pinion focusing motion to the 

 stage of a Microscope of the ordinary type. An additional advan- 

 tage was also secured in this way by making it possible to keep 

 the aperture of the vertical illu- 

 minator attached to the lower end 

 of the body-tube in one position, 

 for which the illuminant and 

 condensers, or optical bench, had 

 been properly and permanently 

 adjusted. Taking a further step 

 in the same direction, the author 

 has designed the present instru- 

 ment with a body-tube rigidly 

 fixed to the limb of the Micro- 

 scope, both the coarse and the 

 fine adjustment being applied to 

 the motion of the stage. 



The general appearance of the 

 instrument will be readily gathered 

 from the illustrations, plate VI. 

 and tigs. 21 and 22, which show 

 the Microscope in three positions ; 

 it will, therefore, only be neces- 

 sary to describe the details of the 

 various special features of the in- 

 strument. 



Base and Limb. — The base is 

 approximately triangular in plan, and has been designed to give 

 the greatest possible stability with a minimum weight, while 

 allowing perfectly free access to the milled heads attached to 



Fig. 21. 



PP 



Pig. 22. 



the stage, even when the latter is in its lowest possible position. 

 A portion of the base projects, and is so shaped as to provide a 

 firm bearing for the limb when the Microscope is being used in 



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