CH. IX] 



MAGNIFICATION IN MICRO-PROJECTION 



257 



Any one can get a pretty correct idea of the screen image and the 

 details visible at different distances by putting the first page of a 

 newspaper up in a well lighted place and then moving back from 

 it. Close up, the ordinary print can be read, farther away the 

 ordinary headlines, and still farther the title of the newspaper or 

 some gigantic headline. Meantime the ordinary print and the 

 ordinary headlines have merged into a gray haze. 



390. Position of the object on the stage. For many micro- 

 scopic specimens it makes no difference how the specimen is placed 

 upon the stage, except that for high powers the cover-glass must 

 be next the objective. If a specimen must have a given part, end 

 or border at the top in the screen image, then with an objective only 

 or an objective and an amplifier, the object must be put on the 

 stage so that the part is down which is to appear at the top in the 

 screen image. With an objective and ocular the object should be 

 placed on the stage as the image is to appear on the screen. For 

 getting the screen image exactly like the object see 36, 512. 



391. Magnification and Screen Image of Various Objectives 

 as Found by Actual Measurement (see 39 ia). 



