ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



Ill 



having them in focus the objective can be changed for a higher homo- 

 geneous-immersion lens. Set the lamp about 20 in. distant from illu- 

 minator (at which distance I get the best resolution), using the sharp 

 edge of the flame, and in horizontal line with opening of illuminator. I 

 use an achromatic lens 2 in. focus as condenser (1 in. in diameter), and 

 put it further away from illuminator opening than focal distance, the 

 opening being open about the thickness of a penny and the light appears 

 on shutters like a ' cat's-eye.' After having light in place and the pin 

 in front of illuminator, to which the reflecting glass is attached, standing 



Fig. 2. 



in an angle of about 45°, you will see only a partially illuminated field, 

 with dark spot in centre ; when you have it so you are ready for work. 



The illuminator can be used only on dry mounts. If you do not 

 vpant to use the illuminator the reflector can be drawn out by the bar in 

 which the pin is. Then it forms only a single patent nose-piece. 



Before putting the light through the illuminator the object should 

 first be brought in focus, using either oblique or central illumination, 

 for lenses of short working distance. The reflector can be set at any 

 angle by turning the milled cap through which the bar passes to which 

 the reflector is fastened. The milled cap is held down by two pins in 

 the cylinder and a groove in the cap into which the pins pass. There 

 are two notches in the cap, which enter into the round groove directly 

 opposite each other. When they are brought in perpendicular position 



