CHAPTER XXI 



RULES FOR HIGH-POWER AND ROUTINE MICROSCOPY 

 HIGH-POWER MICROSCOPY 



1. Have a large enough incandescent surface for the 

 source of light. 



2. Or use double-ground glass (which does not pass 

 direct light) as a radiant. 



3. Have a 3-niillimeter diaphragm close to the source of 

 light, for high powers. Put the object in the spot of light, 

 and focus down. 



4. For ultimate resolution, with high powers, use a light 

 source whose image on the object is much less than the 

 object field. 



5. Employ yellow-green hght filters for the best vision, 

 especially with achromatic or fluorite objectives. Blue- 

 green screens may be used with apochromatics. 



6. Use blue-violet light filters for the largest aperture 

 in photography, with apochromatic objectives. 



7. Control the intensity of the light by a set of screens, 

 preferably yellow-green. 



8. Use a (silvered) reflecting prism instead of a mirror, 

 so as to have only one image of the source. 



9. Adjust the distance of the source of light to suit the 

 corrections of the condenser. If the condenser is made for 

 parallel rays, an accessory achromatic lens must be fitted 

 below it. 



10. Use water immersion for the condenser in daily use. 



11. Employ only an aplanatic well-centered condenser, 

 corrected for color by being achromatic, or by a deep-green 

 screen. 



12. Provide dark-ground stops of the right sizes for the 

 corrected immersion condenser, suited to the low and 



medium objectives. They give an excellent dark field. 



1 .so 



