344 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



Figure 1. Diagram of Photographic Apparatus. (J. natural size.) 



A, sensitive plate or film holder. 



B, box containinof shutter. 



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



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

 support in whicli 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. 

 I, weight, balancing segment. 



J, horizontal projection of revolving shutter in detail. 



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



