266 ORDINARY MICROSCOPE FOR PROJECTION [Cn. IX 



F. S. Feeding screws for the carbons. 



V. A. Vertical fine adjustment for centering the crater. 



L. A. Lateral fine adjustment for centering the crater. 



W t Supply wire to the upper carbon. 



W a Supply wire from the lower carbon through the rheostat (K). 



R Rheostat in the wire from the lower carbon. 



Rods The short tubes or rods supporting the lamp. 



Z,,, L 2 The left and right supports or legs of the lamp-rods. 



Block^ The block on the baseboard to elevate the arc lamp and condenser 

 to the axis of the microscope. 



Lamp-House The metal enclosure of the arc lamp. 



V Ventilator of the lamp-house. 



Condenser The two-lens condenser. It is supported by the front end of the 

 lamp-house. 



/, 2 The two plano-convex lenses forming the condenser. 



Water-cell The glass vessel with plane sides filled with water and placed in 

 the path of the cone of light from the condenser to absorb the radiant heat. 



Microscope An ordinary microscope turned in the horizontal position. The 

 draw-tube and ocular have been removed, also the substage condenser. 



Stage The stage of the microscope. 



SS The substage condenser sleeve. The condenser has been removed. 



Axis, Axis The principal optic axis of the condenser and the microscope. 



() Objective. 



// Handle for carrying the microscope. 



c, f Coarse and fine focusing adjustments. 



cl Clamp for holding the microscope to the block. 



FM Foot of the microscope. 



Block 2 The wooden block supporting the water-cell. 



Block 3 The block to which the microscope is clamped. It moves back and 

 forth on the track (tr). 



tr The rods on the baseboard serving for a track. 



Base Board The board on which all the apparatus is placed. 



395. Stray light, and a water-cell. For a water-cell, any glass 

 vessel with plane sides can be used, and it can be put between the 

 condenser and the stage of the microscope instead of between the 

 lenses of the condenser as in fig. 4, 167. For cutting off stray 

 light one can use a black cardboard shield, or a black disc may be 

 perforated and hung on the end of the tube of the microscope 

 beyond the focusing mechanism. For bellows between the con- 

 denser and stage, use a sheet of asbestos paper. 



396. The directions for using the ordinary microscope in 

 projection arc precisely as for the special microscope shown in fig. 

 121, and discussed in the first part of this chapter. As there is no 

 stage-cooling device one must be careful not to overheat the speci- 

 mens. 



