APPENDIX I 669 
object examined. When using the condenser, employ only the 
plane mirror. 
B. Irs Use: 
1. Place the microscope on the table with the pillar nearest 
you. 
2. Screw the objectives into the nose piece and slip an ocular 
into the upper end, if not already on instrument. Turn the 
lowest power objective into position. 
3. Find the light by looking into the ocular (eye piece) and 
at the same time turning the mirror at such an angle that it 
Fic. 498.—Microscope lamp, useful in illuminating opaque objects. 
reflects light from the window or lamp up through the opening 
in the stage to the objective. When opaque objects are to be 
illuminated, a stronger illumination is required than that usually 
afforded by an ordinary laboratory lamp or by. the light from a 
window. For this purpose a microscope lamp, such as the Bausch 
and Lomb No. 4578 (see Fig. 498) is very satisfactory. Mirrors 
have two faces, a plane and a concave. Use the concave unless 
employing the condenser, when the plane mirror should always 
be used. 
4. Regulate the quantity of light by the iris diaphragm. If 
too bright it must be cut off somewhat. The higher powers 
