THE MICROSCOPE 49 



SUMMARY OF FOCUSING TECHNIC 



Lmv Powers: 



1. Adj\ist low-power objective (No. 3 or 16 mm.) 5 mm. above 



stage. 



2. Arrange mirror so that clear white field is seen. 



3. Place slide on stage (cover-slip upward). 



4. Focus down with coarse adjustment until objective is within 



3 mm. of the slide. 



5. Focus upward with coarse adjustment until object is visible. 



6. Regulate iris diaphragm. 



7. Focus with fine adjustment to bring out details. 

 Changing from Low to High Powers: 



1. Locate object with low power and place it in the center of 



the field. 



2. Focus upward with coarse adjustment until objective is 



about 10 mm. above slide. 



3. Turn high power objective into place. 



4. Increase the diaphram opening. 



5. Focus downward with coarse adjustment until objective is 



about 1 mm. above the slide. 



6. Focus upward with fine adjustment until specimen is apparent. 



7. Regulate iris diaphragm. 

 Cautions: 



1. Never focus downward with coarse adjustment while looking 



in the microscope. 



2. Do not turn the fine adjustment more than five revolutions 



in either direction. 



3. Do no!, change from low-power to hig-hpower objective with- 



out previously raising tube. 



4. In case of accident do not attempt repairs or replacement. 



Use of the Eyes. Contrary to popular opinion, 

 microscopical work is not injurious to the eyes. How- 

 ever, certain precautions must be observed to prevent 

 discomfort and strain. Both eyes should be kept 

 open, as the strain of squinting soon causes headache 

 or tires the eye muscles. By keeping both eyes open, 

 one eye is available for observation of the specimen 

 and the other for transcribing the image to paper. 



