DARK WELLSSTAGE FORCEPS. 8 1 



with the Lieberkuhn are brought out without difficulty. In 

 use, the bull's-eye should be interposed between the reflector 

 and lamp, to render the light parallel, exactly the same as 

 with the parabolic reflector. 



When the object is mounted on an ordinary slide, as a 

 transparent object, a dark ground may be produced by 

 using one of Lister's dark wells, which 

 are merely blackened stops, their deep 

 cup-shape insuring perfect blackness, 

 their diameter intercepting the rays 

 which would otherwise pass into the 

 objective. The engraving (Fig. 65) is 

 an illustration of a dark well in its sub- 

 stage mounting, as made by Messrs. 



T> 1 



Beck. 



For these dark wells the author often uses small circles 

 of black paper mounted on the ordinary 3-inch by i-inch 

 slips, and for most purposes they answer admirably. 



We now come to several very simple but important 

 additions to every microscope, the first of which is generally 

 supplied with all instruments. Fig. 66 delineates the stage 

 forceps, shown holding a fly for rough examination under 



FIG. 66. 



low powers. They are useful chiefly to beginners, with 

 such objectives as the 3-inch or 2-inch, but are altogether 

 unsuitable for high powers. 



In the investigation of minerals it is often necessary to 

 examine small angular pieces which require to be viewed on 



G 



