DESCRIPTION OF THE APPARATUS 69 



municates by means of a large opening with the frame, 



Fig. 46.— Objective mounted in a sliding box. Below can be seen the opening for the 

 passage of the circular diaphragms. 



which contains both the ground-glass plate (Fig. 47) 

 and the negative (Fig. 50). The only parts which call 



Fig. 47.— Frame with ground glass for focussing in chronophotography on fix<d 

 plates. 



for special description are the circular diaphragms, and 

 the shaft which serves to communicate movement to 



