62 
Centering achromatic Condenser. Specially adapted for 
the requirements of photo- micrography, viz for projecting 
a sharp image of the source of light in the plane of the object. 
Fig. 21. 
Centering achromatic Condenser. 
Achromatic condenser of 1.0 num. apert. with iris diaphragm and 
centering adjustment. Made to fit the sleeve of the Abbe illu- 
minating apparatus into which it may be inserted (from above) 
in place of the ordinary (non-achromatic) system (No. 17 a or b). 
Focussing effected by means of the rack and pinion adjustment of 
the Abbe illuminating apparatus 
Achromatic Condenser without centering adjustment and 
also without iris diaphi'agni. Similarly adaptable as No. 20, but 
to be used with the stops forming part of the diaphragm carriers 
