M/CROiSCUl'E OUTFITS 157 



20. The 70 water-immeivsioii of 1.25 aperture, and the 

 90 oil-immersion of 1.3 (or 1.4) aperture, used with com- 

 pensating eyepieces 15, are also good. The 20 of 0.05 

 aperture and the 60 of 1.0 aperture are excellent for routine 

 work. 



9. A triple or quadruple nosepiece with the objectives 

 fairly concentric when in their right places is essential, un- 

 less sliding objective changers are used. 



10. For research (or routine) work without cover-glasses, 

 most of the above objectives can be had from a metallurgi- 

 cal series of short-mounted objectives (Zeiss, Leitz); an 

 appropriate collar, to replace the vertical illuminator, 

 having been added to the microscope. A centering collar 

 can be used on each objective on a double or triple 

 nosepiece. 



Suggested Microscope Outfits for Optimum Work. 

 (A) Routine Microscope for Covered Objects. — Lamp frosted 

 inside (C Mazda), with 3-miUimeter, and larger, dia- 

 phragms. Wratten screens Nos. 66, 56, and 57A. Binocu- 

 lar. Silvered 25- or 30-millimeter reflecting prism. Dry 

 achromatic condenser, corrected for 25-centimeter lamp 

 distance and 1.0-miUimeter slides. Supply of 1.0-millimeter 

 slides. Supply of covers, 0.16 to 0.17 millimeter thick. 

 Apochromatic objective 10. Achromatic objectives; dry 

 40 of 0.85 aperture, with collar, or 50 (or 60) oil immersion 

 of 0.85 to 1.0 aperture, and 90 oil-immersion objective of 

 1.25 aperture. Eyepieces; compensating, 12.5. Achro- 

 matic magnifying lenses, 3 or 4 times. Triplet magnifier, 

 6 times. Screw gage for covers and shdes. 



{B) Routine Microscope for Uncovered Objects. — As in 

 (A), but metallurgical objectives, with a collar of 30 

 miUimeters (or other right length) inserted above the nose- 

 piece (to replace the vertical illuminator, and so give the 

 right tube length). 



(C) Microscope for Achromatic High-power Objectives. — 

 Same as (A) or {E), but with low-voltage high-power 

 lamp with ground-glass disc, water-immersion achromatic 

 condenser of 1.25 aperture, corrected for lamp at 25 centi- 



