59 
Maries 
d) the i 1 1 u m i n a ting appliances described under 
Nos. 20—23. 
The centering collars required for the adjustment of the illu- 
minators 20 to 23 are now supplied with these and are included 
in their prices. 
Fig. 19. 
Centering Collar. 
e) Centering collar for accurately adjusting aclironiatic or 
apoclironiatic objectives used as illuminators in photo-micrography. 
As most of these appliances require adjustment to the plane 
of the object, every Abbe illuminator now made is fitted with 
rack and pinion for adjustment in the direction of the optic axis. 
Every microscope fitted with it may, therefore, be used in con- 
junction with any other form of illuminator which 
may be required. 
