To Determine Magnifying Power. While 

 the magnifying power may be known from tables 

 accompanying the microscope, these are only approx- 

 imate, as there is more or less variation in eyepieces 

 and objectives and furthermore the microscope may be 

 used under different conditions from those under which 

 the original determinations were made. 



To determine magnifying power three requisites 

 are necessary : 



A camera lucida. 



A stage micrometer ruled in divisions of inches or 

 millimeters. 



A pocket or foot rule in inches or millimeters, 

 according to the stage micrometer which is used. 



The stage micrometer is a glass slip having a very 

 fine scale ruled upon it. The lines are often so fine as 

 to be nearly invisible except under the microscope. 



Place the stage micrometer with divisions ofo.oi mm. 

 upon the stage and focus. Attach 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 drawing paper ; mark the spaces 

 of the micrometer as projected upon the paper and 

 determine how many of the divisions of the rule are 

 contained within one or more spaces on the paper. If 

 the values are in millimeters and it should be found 

 that 25.0 mm. on the rule are contained in one space 



