VERTICAL ILLUMINATORS, METALLURGICAL MICROSCOPES 89 



cessively preparations of greatly varying thickness. Fig. 38 

 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 prepa- 

 rations for examination with vertical illuminators so that when 

 placed upon the stage of the microscope, the upper or polished 

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

 microscope, proceed as follows: place upon a 1 by if inch extra 

 thick object slide of metal or glass a small piece of soft plasticine, 

 soft beeswax or soft paraffin; lay the object to be studied pol- 

 ished 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 glass object slide upon the stage 

 of the microscope and then carefully raise the preparation by 

 means of the substage screw until it is 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 exami- 

 nation with the vertical illuminator. Special mounting cells 

 employing this same principle have been designed. 



One of these cells or devices is shown in Fig. 39. 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 spec- 

 imens of different thicknesses. The spec- 

 imen to be mounted is laid upon a piece of 

 lens paper, polished side down upon the bed 

 piece. The collar is then raised or lowered the 

 proper amount and an object slip carrying a 

 bit of plasticine is inverted over the prepara- 

 tion and pressed down until each end touches 

 the circumference of the collar. The slip may now be lifted off, 

 carrying with it the specimen imbedded in the plasticine or 

 wax. Laid upon the stage of the microscope, the polished sur- 



Fig. 3Q. Device for 

 Mounting Pieces of 

 Polished Metal for 

 Study with Vertical 

 Illuminators. 



