PRELIMINAEY EXERCISES. 3 



D. The Use of the Microscope. 



1. To get the light. 



Place the microscope with the vertical column next to 

 you, the eye-piece in position. Look through the 

 eye-piece and move the mirror until you obtain 

 a bright circle of light (field of vision) similar to 

 that obtained when you held the eye-piece to the 

 light. 



2. To focus. 



Place a mounted preparation on the stage of the 

 microscope exactly over the center of the open- 

 ing. Remove the sliding tube. Take the low 

 power firmly in your left hand and screw the 

 sliding tube on to it. Replace the sliding tube, 

 and, bending over so that your eye is on a level 

 with the stage, slowly lower the sliding tube by 

 means of the coarse adjustment until it is within 

 a centimeter of the stage. Then, looking through 

 the eye-piece, raise the sliding tube by means of the 

 coarse adjustment until the object comes into view. 

 Next, by means of the fine adjustment, raise or 

 lower the sliding tube until the outline of the 

 object is sharp and clear. Repeat this until you 

 become skilful. (Turn the milled head with the 

 thumb and fore-finger. Never make more than 

 three revolutions of the milled head in the same 

 direction. ) 



Substitute the high power and proceed as follows : 

 With your eye on a level with the stage as before, 

 lower the sliding tube by means of the coarse 

 adjustment to within a millimeter of the object. 

 Then by means of the fine adjustment raise the 

 sliding tube until the outline of the object is 



