PHOTOMICROGRAPHY 269 



own construction. Projection eye-pieces, Nos. 2 and 4 (see Fig. 105) 

 were used in conjunction with these lenses. 



The microscope, electric lamp, and other fittings connected therewith, 

 just described, are placed on a slide on a table as shown in Fig. 102, 

 while the camera is placed on a separate stand (see Fig. 102). 



For sunlight a light filter is used, while with the electric light 

 spectroscopic-tested glass plates are used for red stained specimens, 

 green ; for blue stained specimens, yellow ; for violet, yellow, and green, 

 and for unstained specimens, blue. 



For focusing the image on the ground glass of the camera a special 

 improved aplanatic focusing lens is used with an exceptionally large 

 field and a magnification of 6 a higher power is a disadvantage. The 

 fine adjustment during focusing is manipulated by means of a Hook's 

 key and rod connection. 



Magnification. This depends upon the distance of the specimen from 

 the ground glass slide, and can be accurately measured as follows : Take 

 a stage micromillimeter (which is one millimeter divided into hundredths) ; 

 place it under the lens and project the picture on the ground glass slide ; 

 adjust the focus, and measure the size with an ordinary glass 100 milli- 

 meter measure. When 1 millimeter of the projected stage micrometer 

 is equal to 10 millimeters on the glass measure, then the magnification = 

 1000 diameter. Other magnifications are calculated in a similar manner. 



