THE MICROSCOPE 



67 



Use of the Microscope. Position. 1. Always use the 

 microscope with the tube in the perpendicular position. 

 This is indispensable in examining fresh mounts or fluids. 



2. Work with both eyes open and if possible use both 

 eyes interchangeably. 



Light. 3. Never use direct sunlight. The best light is 

 obtained from white clouds. Northern or eastern light is 

 preferable. 



The best artificial light is a Welsbach burner (gas). 

 When employing artificial light use a blue glass between 



FIG. 23. Double Demonstration Ocular with Pointer Enabling Two 

 Observers to View Simultaneously the Image Indicated by the 

 Adjustable Pointer. 



the light source and the specimen. Often an eye-shade 

 or some appliance with a similar purpose is desirable. 



4. Use the plane mirror in daylight, the concave mirror 

 with artificial light. 



Focusing. 5. After putting in place a low-power ocular 

 and objective, place the specimen on the stage, and while 

 looking through the microscope, adjust the mirror so as to 

 illuminate the field as evenly as possible, but not so brightly 

 as to irritate the eyes. 



6. By means of the coarse adjustment, focus the body 

 tube until the objective nearly touches the cover-glass, 

 being careful not to touch it. 



