VERTICAL ILLUMINATORS, METALLURGICAL MICROSCOPES 99 



Metallurgical Microscopes for the Examination of Large 

 Castings, etc., are now manufactured by a number of different 

 firms. Such instruments are often designated, as "Works 



Microscopes/' since their purpose is 

 the study of materials of construction 

 already in place or too large to bring 

 into the laboratory. 



FIG. 47. Stead Works Micro- 

 scope. 



FIG. 48. Tassin Metallurgical Microscope. 



As indicated by the name and purpose they are compact, sub- 

 stantially built and easily transportable. They consist essen- 

 tially of a compound microscope, whose pillar or handle arm has 

 been separated from the remainder of the instrument in a line 

 in the plane of the stage, and attached to a suitable base or to 

 three legs. In other words, these instruments are microscopes 

 without stage or substage. When in use, the base rests upon 

 the object to be studied and the tube carrying objective, illumi- 

 nator and ocular is raked down until the surface of the object 

 is in focus, there being an aperture in the base in line with the 

 optic axis or the base is provided with widely divergent legs. 

 Figs. 47, 48 and 49 illustrate typical instruments of this class. 



