CH. IX] 



TROUBLES WITH MICRO-PROJECTION 



303 



FIG. 168. THOMPSON'S PROJECTION MICROSCOPE. 

 (Cut loaned by the A. T. Thompson Co.). 



The projection microscope with the substage condenser system is attached 

 to the reflectoscope (rig. 97) in the position where vertical opaque objects are 

 placed ; this allows the direct beam of light to be utilized in micro-projection. 



The stage and the objective holder are independent, and no ocular is used. 

 This permits the projection of large objects with low powers or smaller objects 

 with high powers. From the short tube employed, the field is not restricted. 



its position often work wonders. The substage condenser 

 may be too near to the large condenser or too far from it 

 so that the light cone does not reach it in its most favorable 

 position. 



4. The room may not be dark enough or external light may fall 



directly on the screen from some window or open door. 



5. Never forget the carbons. A slight mal-position or decen- 



tering of the crater may cause all the trouble. 



