MOVING PICTURES 451 



motor. These pictures are thrown upon the screen at the 

 same rate at which they are taken, about sixteen per second. 

 After the film has been used, it must be rewound on another 

 reel, so as to bring the first picture into its proper position 

 again. 



FIELD EXERCISE 8 



Purpose. To visit a moving picture theater to see how the 

 projecting apparatus works. 



Directions. Arrangements should be made with the manager of 

 some moving picture theater to have the class visit the theater 

 when it is not being used, in order to see how the projecting ma- 

 chine works. The operator can explain the details of the opera- 

 tion. At the next meeting of the class the points observed should 

 be discussed. 



Physiology of moving pictures. In order to understand 

 the action of the moving pictures, we must not only under- 

 stand the camera by which they are taken, and the pro- 

 jector by which they are thrown on the screen, but also the 

 eye which sees them. The machine throws on the screen 

 about sixteen pictures a second, which occupy a foot of film. 

 The screen is darkened about half the time. Why do we 

 not see these as so many distinct pictures, instead of as a 

 continuous series of moving pictures? This is due to a 

 peculiarity in the action of the eye. Rays of light pass 

 through the pupil and are focused by the lens on the retina 

 of the eye. This is lined with a network of sensitive nerves, 

 so that when the image is formed here, impulses pass to the 

 brain, and we have the sensation of sight. Even after the 

 object is removed from view, the image still lingers in the 

 brain for about one twenty-fourth of a second, just as though 

 the object were in full view. In the movies the pictures are 

 shown so rapidly that the second picture is shown before the 

 image of the first leaves the brain. Thus the brain sees a 

 continuous series of pictures without any breaks between, 



