VERTICAL ILLUMINATORS, METALLURGICAL MICROSCOPES 89 



centering screws and lifting out the stage. An "auxiliary" 

 stage is then inserted in the substage ring, the specimen placed 

 upon it and the focusing is done by means of the substage quick- 

 acting screw. Delicate focusing may then be made by the fine 

 adjustment of the microscope. This method possesses the ad- 

 vantage of producing no disturbance of the alignment of radiant 

 and reflector in changing objectives or in studying successively 

 preparations of greatly varying thickness. Fig. 41 illustrates 

 the chemical microscope with auxiliary stage applied for the 

 examination of opaque objects. The auxiliary stage itself is 

 shown at A. 



Mounting Polished Objects. In order to mount small 

 preparations for examination with vertical illuminators so that 

 when placed upon the stage of the microscope, the upper or pol- 

 ished surface will lie in a plane at right angles to the optic axis 

 of the microscope, proceed as follows: place 

 upon a i by i \ inch extra thick object slide 

 of metal or glass a small piece of soft plas- 

 ticine, soft beeswax or soft paraffin; lay the 

 object to be studied polished side up upon 

 the imbedding material and place the prepa- 

 ration upon the substage ring (with auxiliary 



stage in place if one is at hand) ; place a thick ~ '. , 



r FIG. 42. Device for 



glass object slide upon the stage of the micro- Mounting Pieces of 

 scope and then carefully raise the preparation Polished Metal for 

 by means of the substage screw until it is Study with Vertical 



- . , . i.,. Illuminators. 



pressed firmly against the object slide, the 

 latter being held in place with the fingers. The upper surface 

 of the object to be studied is thus made parallel to the plane of 

 the stage and is in proper position for examination with the 

 vertical illuminator. Special mounting cells employing this 

 same principle have been designed. 



One of these cells or devices is shown in Fig. 42. It consists 

 of a bed plate attached to a base and threaded to carry a collar 

 screwing up and down. The upper edge of the collar is exactly 

 parallel with the surface of the bed plate. The collar is screwed 

 up or down to accommodate specimens of different thicknesses. 



