PHOTO-MICROGRAPH} 



[CH. 



modern achromatic objectives were found to give excellent results when used 

 without an ocular. Most of them also gave good results with projection 

 oculars. It must be said however, that the best results were obtained with the 

 apochromatic objectives and projection oculars. It does not seem to require 



FIG. 171. Vertical 

 photo-micr graphic cam- 

 era, screen and small table 

 The table is about 45 cen- 

 timeters high and in the 

 legs are large screw eyes 

 for leveling screws. The 

 operator can stand on the 

 floor and perform all the 

 necessary operations, and 

 in adjusting the micro- 

 scope can sit on a low 

 stool. 



The screen is of zinc 

 and has two heavy lead 

 feet to hold it steady. 

 Near the lower left hand 

 corner of the screen is an 

 aperture for the light to 

 shine through upon the 

 mirror. This opening is 

 closed by a black slide 

 which is just balanced so 

 that it slays in any posi- 

 tion. In making the ex- 

 posiire it is raised suffi- 

 ciently to admit the light 

 to the mirror, but the 

 stage is left in shadou*. 

 This screen shades the 

 microscope and the face 

 of the operator. ( Trans. 

 Amer. Micr. Soc. sooi.) 



so much skill to get good results with apochromatics as with achromatic ob- 

 jectives. The majority of photo-micrographers do not use the Huygenian 

 oculars in photography, although excellent results have been obtained with 

 them. An amplifier is sometimes used in place of an ocular. Considerable 

 experience is necessary in getting the proper mutual position of objective and 



