492 Prof. Richards and Mr. Archibald : A Study of 

 Fig. 1. — Diagram of Photographic Apparatus. (\ natural size.) 



A, sensitive plate or film-holder. 



B, box containing shutter. 



0, pulley attached to axle of shutter to communicate power from motor. 



D, light rod moved by crank attached to same axle ; D is guided by a stout 



support in which it moves loosely. 



E, segment provided with ratchet-teeth ; moved gradually by rod D. 



F, microscope. 



G, slide for object, moved by wire running to H. 

 H, holes to regulate amplitude of object's motion. 



1, weight, balancing segment. 



J, horizontal projection of revolving shutter in detail. 



The diagram represents the apparatus an instant before an exposure begins. 



