XXU INTRODUCTION 



V. Arrange the mirror so as to throw the light lehich 

 comes in at the window up through the opening in the mid- 

 dle of the stage. Do not use the direct sunlight. 



8. Place the glass slide on the stage and under the clips, 

 with the object over the centre of the opening. If the ob- 

 ject be mounted in a fluid, see that none of the latter oozes 

 out around the edge of the cover-glass, otherwise the objec- 

 tive may be soiled. Never use the high power to examine 

 an object which is not protected by a cover-glass. 



9. Turn the tube down nearly to the object. 



10. While looking through the microscope, bring the ob- 

 ject into focus by slowly turning the tube upward. Never 

 do so by turning the tube downward. 



11. Examine every object with the low power first; keep 

 both eyes open when examining an object. This can be 

 done after a little practice, and avoids unduly fatiguing the 

 muscles which close the unused eye. Get into the habit of 

 using either eye. With the low power use a large and with 

 a high power a small diaphragm. Use the concave mirror 

 for strong illumination. If foreign particles appear in the 

 field, locate them by the following method : While looking 

 into the instrument rotate the eye-piece in the tube ; if the 

 particles also rotate, they are on or in the eye-piece and 

 should be removed; if the particles do not rotate, move the 

 slide; if the particles move, they are on the slide and must 

 be wiped off. If the object looks hazy, the particles must 

 be on the objective, which may be gently wiped; if this does 

 not remove the difficulty, take the instrument to the in- 

 structor. While observing, vary the focus constantly with 

 the fine adjustment. This method will give a far clearer 

 idea of the object than to fix the focus once for all and to 

 sit staring into the tube. 



12. On quitting work, turn the tube up to about an inch 

 above the stage, remove the slide, unscrew the objective 

 and put it into its case, remove the eye-piece and return 

 it to the box, straighten the instrument if it has been in- 



