348 DRAWING WITH HOUSE CURRENT [Cn. X 



To start with, the substage condenser diaphragm should be 

 opened widely. In some cases the picture can be made sharper by 

 afterward closing the diaphragm somewhat. 



For drawing, a skillful use of the substage condenser is very 

 important. One must be more precise in its use than in ordinary 

 microscopic observation. 



FIG. 194. DRAWING WITH A MICROSCOPE WITH THE ARC LAMP AT RIGHT 



ANGLES. 



In this picture a prism is placed beyond the ocular to reflect the light down- 

 ward (fig. 192). The arc lamp is on the back side of the microscope with the 

 condenser facing the mirror. The spot of light on the shield or disc above the 

 lamp shows that the light is not centered along the axis of the microscope. 

 The mirror must be turned slightly until the light reflected back from the 

 substage condenser and microscope mirror enters the condenser tube of the 

 arc lamp (see fig. 195). 



500. Plane mirror and substage condenser. Use the plane 

 mirror and substage condenser for all objectives of 12, 10, 8, 6, 4, 

 and 2 mm. equivalent focus. 



501. Concave mirror and substage condenser. For the 16 to 



1 8 mm. focus objectives use the substage condenser with the con- 

 cave mirror. It may also be necessary to separate the condenser 

 somewhat from the preparation to light the entire field. 



