169 



measurement was 30.0 mm. the enlargement 

 would be 30 times 100 divided by 10, or 300. If a 

 standard of 10 inches is maintained in all drawings 

 and the amount of magnification with certain 

 objectives and eyepieces be previously determined 

 by means of the stage micrometer, a standard is 

 established for each and further measurements 

 will not be required. If however, variations from 

 this standard distance are made, the actual magni- 

 fication should always be determined. 



To Determine Magnifying Power. While 

 the magnifying power may be known from tables 

 accompanying the microscope, these are only 

 approximate, as there is more or less variation in 

 eyepieces and objectives and furthermore the 

 microscope may be used under different conditions. 

 There are three requisites. 



A camera lucida. 



A stage micrometer ruled in divisions of indies or 

 millimeters. 



A pocket or foot rule in indies or millimeters, 

 according to the stage micrometer which is used. 



If a low power objective is used, place the stage 

 micrometer with divisions of 0.1 mm. or 0.01 inch 

 upon the stage and focus. After attaching the 

 camera lucida, place the microscope in exactly the 

 same position as for drawing, maintaining the 

 standard distance of 10 inches from optical axis to 



