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 i by 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 carr3dng 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. 
