THE USE OF THE MICROSCOPE 



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photographs arc 



RULEK NeAKLY 



8. High-power 



poor. 



9. Objects have to be stained 



deeply to show up in the glare. 



10. Balsam mounting is usually 



essential for clear images. 



11. Out-of-center objectives may 



spoil images. 



Rules Neakly All Attendki) 'I'o 



Excellent high-power photographs 



of flat objects can be made. 

 Feebler staining can be used, so as 



to be more or less transparent. 

 Watery fluids, as well as balsam, may 



be used for mounting. 

 Accurate centering of high objectives 



ensures optimum images. 



Most workers find themselves between these two 

 extremes. There is no reason why every microscopist 

 should not closely approach the optimum, if time for 

 the necessary amount of extra care can be afforded. 



Causes of Injury to the Microscopical Image. — A list 

 of some of the errors causing deterioration of the image in 

 the microscope is given below. The apparently simple 

 matter of soiled surfaces of lenses is included, because 

 experience has shown that incessant vigilance alone can 

 secure some approach to optically clean lens surfaces on a 

 microscope in constant use. In this list, the items regarded 

 as especially deserving the attention of the microscopist 

 (even the routine worker) are in italic type. (Some of the 

 other items are to be recommended only for particularly 

 accurate work, and these are put in square brackets.) 



Causes of Injury 



Preventive 



Neutral screen, or yel- 

 low-green light filter. 



Lamp of higher wattage, 

 or better corrected or 

 better centered con- 

 denser. 



Large enough disc of 

 double-ground glass 

 near lamp. 



Small enough dia- 

 phragm close to light. 



Circular diaphragm on 

 source. 



Put lamp at estimated 

 distance. Use ring 

 test. 



