l] THE USE OF THE MICROSCOPE 



the higher ocular 90 to 100 diameters. Examination 

 with a magnification not greatly outside these limits is 

 spoken of as examination under a low power of the 

 microscope. 



3. (a) Substitute the th inch object-glass for the 

 trd inch ; and the No. 2 ocular for the No. 4. Lower 



3 



the tube with the coarse adjustment until it is 

 about J inch from the cover-slip. Use a diaphragm 

 with a small aperture, and adjust the mirror so as to 

 obtain as much light as possible. Look through the 

 ocular, and slowly lower the tube with the fine adjust- 

 ment, until the specimen is brought into view. 



It aids in catching sight of the specimen, if the 

 slide is moved a trifle to and fro, as it is being brought 

 into focus. 



When the specimen is in focus, note carefully the 

 distance of the object-glass from the cover-slip. 



Substitute ocular No. 4 for ocular No. 2; focus with 

 the fine adjustment, and note the increase in magnifi- 

 cation, and the decrease in the amount of light in the 

 field. 



The magnification of the th obj. with the lower 

 ocular will probably be 250 to 280 diameters, with the 

 higher ocular about 400 diameters. Examination with 

 a magnification of about 250 or more is spoken of as 

 examination with a high power of the microscope. 



(6) Raise the tube, then looking from the side, 

 lower the tube with the coarse adjustment until the 

 object-glass nearly touches the cover-slip. Look through 

 the ocular, and slowly raise the tube by the fine ad- 

 justment until the specimen is focussed. 



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