THE LIEBERKUHN CONDENSEK. 



65 



Specula, known as Lieberkuhn's, are much employed, and preferfed by 

 some mioroscopists. The Lieberkuhn is concave, and attached to the 



fig. 42. 



object-glasses, from the two-inch to the half-inch, in the manner repre- 

 sented at fig. 4:3, where a exhibits the lower part of the compound 

 body; b the object-glass, over which is slid a tube and the Lieber- 

 kuhn c attached to it ; the rays of light re- 

 flected from the mirror are brought to a 

 focus upon an object d, placed between it 

 and the mirror. The object may either be 

 mounted on a slip of glass, or else held in 

 the forceps /; and when too small to fill up 

 the entire field of view, or when transparent, 

 it is necessary to place behind it the dark 

 well e. 



Each Lieberkuhn being mounted on a 

 short piece of tube, can be slid up and down 

 on the outside of the object-glass, so that 

 the maximum of illumination may be readily 

 obtained. In the higher powers the eml of 



F 



-~^ 



fig. 43. 



