HIGH-POWER AND ROUTISE MICROSCOl'Y 189 



42. Have the mounting media as close in refraction to 

 1.33 or 1.52, respectively, as possible (in most cases). 



44. Measure the cover-glasses on the preparations with 

 the fine motion of the microscope, or with a screw gage 

 before mounting. 



45. Keep the microscope under a bell jar with a vessel 

 of fused calcium chloride, in damp weather. 



4G. Keep the objectives, when not in use, in a dessicator 

 over fused calcium chloride, in tropical climates especially. 



47. Have a sliding bar or a screw object traverser on 

 the microscope stage. 



48. Use a corrected pocket magnifier of 3 to 10 times for 

 examining the objective lenses for cleanliness. 



49. Use a Steinheil magnifier of 10 to 16 times to magnify 

 the eyepiece circles. 



50. Test the optical performance of the microscope with 

 the high objectives regularly, and keep it up to the 

 standard. 



ROUTINE MICROSCOPY 



1. Use a C-Mazda lamp, frosted internally, as a radiant; 

 with a clear, yellow-green or blue, light filter, and an iris 

 diaphragm. 



2. Have a dry achromatic condenser, corrected for lamp 

 distance and for slides 1 miUimeter thick. Focus the 

 radiant on the slide. 



3. Use only slides 1 millimeter thick, for important work. 



4. Use only covers 0.17 millimeter thick, for important 

 work. 



5. If no covers are used, pull out the tube (or eyepiece) 

 about 15 millimeters, with the 90 oil-immersion objective, 

 for optimum observation. 



6. Use (neutral or) yellow-green screens to moderate the 

 light. 



7. The oil-immersion objective of about 1.0 aperture 

 can often replace that of 1.3 aperture, with advantage. 



8. With high powers, contract the iris on the source of 

 light, to cut off glare. 



