28 Modern Microscopy 



Three screws permit of any want of parallelism between 

 the faces of the specimen being compensated for. 



To illuminate a specimen a vertical illuminator, the con- 

 struction and use of which is referred to on page 105 and 

 which may be fitted at either the eye or objective end of the 

 body-tube, is employed. The lamp and bull's-eye have to 

 be placed in fixed relation to this vertical illuminator, and 

 it is important that once the illuminant is adjusted no more 

 than a slight movement, such as would be imparted by the 

 fine adjustment, should take place ; this renders obvious the 

 utility of the rack-work for raising and lowering the whole 

 of the mechanical stage. Other microscopes for the same 



Fig. 12. — Holder foe Metalluegical "Woek. 



specific purposes are made by C. Keichert, of Vienna, and 

 Queen and Co., of Philadelphia. 



The necessity for a special microscope for metallurgical 

 work has, to a certain extent, been obviated by the introduc- 

 tion of a carrier, which can be constructed to fit any ordinary 

 microscope stage. It is shown in Fig. 12. The subject 

 for examination is held between two jaws, which can be 

 made to approach or recede from each other by means of 

 ecrews, to which they are attached, the block of metal under 

 examination is gripped between the jaws, and can be set 

 at any desired angle. This is particularly useful where 

 large surfaces are required to be gone over or where the 

 face of a cylindrical piece of metal is to be inspected, the 

 cylindrical portion itself being suspended through the 

 aperture in the stage. The addition of the vertical 



