84 



ELEMENTARY CHEMICAL MICROSCOPY 



FIG. 35. Leitz Vertical 

 Illuminator. 



lens L in its mounting C. C slides within T, thus permitting 

 regulation of the diameter of the illuminating beam of light 

 projected upon the reflecting surface. One side of K is flattened 



and through this surface is cut an 

 opening into the interior of the cell. 

 The lower part of this opening is 

 dovetailed as shown at d. The 

 prism P and the disk k are attached 

 respectively to the axis of the milled 

 wheels W and W'. These in turn 

 are mounted upon metal plates with 

 edges obliquely cut so as to fit into 

 the dovetail d. These plates when 

 inserted and pressed in place are 

 held by the spring s. They are thus 

 secured in proper position but can 

 be slid back and forth in the slot d. 

 A mark S upon the plates and an- 

 other / upon the adapter serve to 

 indicate the proper position of P or k with respect to the optic 

 axis of the microscope M. To remove the prism, the wheel 

 W is pressed gently downwards and outwards, thus releasing 

 the plate from the spring s; W is then carefully raised until 

 the plate is free from the slot d. It can then be removed by 

 tipping up slightly and withdrawing from the opening. To insert 

 the disk, turn W' until the groove i is horizontal, introduce k into- 

 the opening and push down till the lower edge fits into J, then 

 press W' forward as far as it will go. The groove S is then brought 

 into coincidence with /. The reflecting disk k is fastened to a 

 mounting by the spring fingers v. This device permits the rapid 

 and easy removal of the disk for cleaning or for replacement 

 when broken. The objective O is screwed into the lower open- 

 ing of K ; O in the illustration is an 8 millimeter apochromatic, 

 for 200 millimeters tube length, uncorrected for cover-glasses. 



Just as in the simple prism or disk illuminators, the rays of 

 light striking the reflecting surface are directed downwards 

 through the objective upon the object m. 



