ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



20' 



are inclined to one another at 165°, the optical axes being at 15°. The 

 screens work in grooves p, and are stopped off by two circular stops of 

 50 mm. in diameter. Thus the projected image also has a diameter of 

 50 mm. The width of the camera is 150 mm. The screens are the 



Fig. 23. 



ordinary commercial slides of 9 by 6 cm. ; they are secured in their 

 frame by a buckle w. 



The camera can be exchanged for the tube of a preparation-Micro- 

 scope on the same stand. For this purpose the plug m fits into a hollow 

 cylinder, which, itself, is an arm of the cylinder k working between 



