MICROSCOPE OUTFITS 155 



Their use saves much time, with the dry condenser 

 especially. 



9. Have cover-glasses previously measured by the 

 screw gage, and 0.17 millimeter thick, for important 

 objects. This saves the time needed for adjusting tube 

 length. 



10. Have the objectives made as accurately concentric 

 as possible on the revolving nosepiece, so that the field 

 requires a minimum of shifting on changing powers. 

 This is important for quick work. 



11. Have a revolving nosepiece which takes in all the 

 objectives required, so as to avoid unscrewing, and to allow 

 of accurate centering of each objective. Three or four 

 objectives are enough for most work. 



12. Use a mechanical stage without scale and verniers 

 for most biological work. There are quicker ways of 

 finding objects than with scales and verniers. 



13. Time may easily be wasted in testing objectives. 

 If an objective stands a 91 o cone without glare on stained 

 objects with accurately adjusted condenser, and gives 

 good definition with the calculated maximum useful 

 eyepiece magnification (such as 12.5 for the 100 fluorite 

 objective, and 15 for the 90 apochromatic), it does not need 

 testing, if it is accurately centered. 



14. The use of water-immersion objectives saves time 

 otherwise spent in cleaning covers from immersion oil, 

 when going over sUdes with large covers, with objects in 

 watery fluids or iron-acetocarmine. 



15. The disuse of cover-glasses with short-bodied oil- 

 immersion objectives used on smears, etc., may save much 

 time. 



16. Changing eyepieces may waste time, and may bo 

 reduced to a minimum ; for one optimum eyepiece can often 

 be used throughout. 



17. Altering tube length wastes time, and a fixed tube 

 length is often best for routine work, cover-glasses being 

 measured previously. 



