HIGH-POWER AND h'OVTfXE MfrROSfOpy 195 



green screen. Searoli the slide, and find ()l)ject for higli 

 power. Put a 3-millinieter diaphragm on the source. 

 Center it, focus it, and increase the condenser aperture. 

 Put immersion oil on the lighted spot on the slide, as well 

 as on the front lens of the oil-immersion objective. Focus 

 down the immersion objective, looking outside till the oil 

 runs in by capillary attraction. Raise the objective 

 slightly to make sure it is not below the focus. Lower 

 objective until object or diaphragm edge is visible. Center 

 object. Focus and center diaphragm. Look at eyepiece 

 circle with 10-times magnifier, and open condenser iris 

 sufficiently. Apply suitable yellow-green or blue-green 

 screen. Slightly change iris and condenser focus for 

 optimum vision. After observing, raise objective, and 

 then revolve it. (Clean off immersion oil before leaving 

 microscope.) 



