262 



PROJECTION MICROSCOPE 



[CH. IX 



For the minute details of a projected specimen it is recommended 

 that the audience use opera glasses. These are also useful for the oper- 

 ator in focusing the image on the screen. 



TABLE SHOWING THE SIZE OF OBJECT, THE MAGNIFICATION 

 AND THE SIZE OF THE SCREEN IMAGE WITH VARIOUS 

 OBJECTIVES AND PROJECTION OCULARS 



Distance oj the screen from the stage of the microscope, 8 meters (26 feet +). 

 Arc tight, 12 ampere current, for illumination. 



Objective 



Projection 

 Ocular 



Achromatic 

 Condenser 



Actual Size of 

 Field 



Magnification 



Diameter 



of Screen 



Image 



64 mm. 



none 



none 



20 mm. 



125— 



250 cm. 



42 mm. 



none 



none 



10 mm. 



185 



185 cm. 



35 mm. 



none 



none 



9 mm. 



230 



207 cm. 



24 mm. 



none 



none 



7 mm. 



335 



235 cm. 



18 mm. 

 " mm. 

 " mm. 



none 



X 2 



X 4 



none 

 condenser 

 condenser 



6 mm. 

 1.5 mm. 

 1.5 mm. 



440 



860 



1640 



264 cm. 

 130 cm. 

 245 cm. 



16 mm. 

 " mm. 

 " mm. 



none 



X 2 



X 4 



none 

 condenser 

 condenser 



4 mm. 



1.25 mm. 



1 mm. 



53° 

 1090 

 2040 



200 cm. 

 136 cm. 



204 cm. 



8 mm. 



" mm. 

 " mm. 



none 

 X 2 



X 4 



condenser 

 condenser 

 condenser 



3+ mm. 

 0.60 mm. 

 0.60 mm. 



1000 

 2250 

 4500 



300 cm. 

 140 cm. 

 270 cm. 



6 mm. 

 " mm. 

 " mm. 



none 

 X 2 

 X 4 



condenser 

 condenser 

 condenser 



2 mm. 

 0.50 mm. 

 0.50 mm. 



1200 

 2550 

 5000 



240 cm. 

 130 cm. 

 250 cm. 



5 mm. 

 " mm. 



none 

 X 2 



condenser 

 condenser 



1.80 mm. 

 0.40 mm. 



1750 

 3500 



300 cm. 

 140 cm. 



4 mm. 



none 



condenser 



1.50 mm. 



2150 



320 cm. 



3 mm. 



none 



condenser 



1 mm. 



2350 



235 cm. 



2 mm. 



none 



condenser 



0.60+mm. 



4000 



300 cm. 



§421. This table shows approximately the size of object which 

 each objective will project upon the screen. This was determined ex- 

 actly as described in § 50. For the magnification one simply measures 

 the distance between two or more lines of the image of the microm- 

 eter on the screen, and divides the size of the image by the known 

 size of the object ( §155). An)' good stage micrometer will answer. 

 It is necessary, however, to use one with coarse lines for the low pow- 

 ers (§ 159, 170). 



By comparing the magnification with and without the projection 

 oculars, and also comparing the size of object which can be projected 





