336 



[Cn. X 



FIG. 187. AN ORDINARY MICROSCOPE USED WITH THE LAMP AND 

 CONDENSER OF A MAGIC LANTERN FOR DRAWING OR PROJECTION. 



W The supply cable from the outlet box (fig. 3). 



s The table, knife switch. 



r Rheostat of the theater-dimmer type. 



/ The automatic arc lamp. This is the three-wire automatic arc lamp of 

 the Bausch & Lomb Optical Company for 5-25 amperes. (For the method 

 of connecting the wires see 704). 



c Triple condenser with water-cell. 



a a Principal optic axis. 



p The concave parallelizing lens to render the converging cone from the 

 condenser parallel or nearly so before entering the sub stage condenser of the 

 microscope. 



m The microscope in a horizontal position. If it is to be used for drawing 

 there must be a prism or mirror beyond the ocular to reflect the light down on 

 the drawing shelf. 



b Baseboard with track serving as an optical bench. 



a s Adjustable drawing shelf on the front of the projection table. 



proximately parallel light (fig. 150 A. B.), hence it is necessary to 

 render the converging cone of light from the main condenser 

 approximately parallel. This is most easily accomplished by using 



