CH. IX] ORDINARY MICROSCOPE FOR PROJECTION 267 



I h 



FIG. 147. PROJECTION WITH THE MICROSCOPE IN A VERTICAL POSITION. 



W vSupply wires from the outlet box (fig. 3). 



r Rheostat of the theater-dimmer type. 



t w Wires to the arc lamp from the switch. 



/ a Fine adjustment screws projecting behind the lamp-house. 



h f Hand-feed screws for the carbons of the arc lamp. 



/ h Lamp-house. It is of sheet iron, but was left in position only a part of 

 the time, hence it appears transparent. 



g Observation window opposite the crater. 



C Triple condenser with water-cell (fig. 121). 



a a Principal optic axis. The mirror of the microscope reflects the light 

 vertically along this axis and through the microscope, then the mirror or prism 

 over the ocular reflects it horizontally again. 



m Mirror or prism over the ocular to reflect the light horizontally to the 

 screen. 



sh Shield to cut off stray light. 



b Baseboard with track for an optical bench. 



a s Adjustable shelf for drawing. 



