584 



Our Surroundings 



alarm attached to the cell. The "electric eye" is also used to 

 detect slight differences in color, and it plays an essential part in 

 talking motion pictures, in sending pictures by telegraph or radio, 

 and in television. It will be interesting for you to find out how 

 many new inventions have been made possible by this one useful 

 device the photoelectric cell. 



Talking Motion Pictures. What is the chief difference 

 between the motion pictures of today and those of a few years 



Brown Brothers. 



PART OF A TALKING PICTURE FILM 



Both the picture and the sound are recorded on this film. Notice the sound track at 



the left of the picture. The holes in the outer edges of the film fit over the teeth 



of a series of cog wheels which move the film through the motion-picture machine. 



ago? Sound, of course. The actors in those days were seen but 

 not heard. Today, we not only see the actors but hear their voices 

 as well. How is this done? 



Talking motion pictures are of two kinds. The simpler form 

 consists of a series of phonograph records, made at the same time 

 that the pictures are taken. The film registers what the actors do 

 and the records register what they say, as well as any sound 

 effects which are made to accompany the action. When the pic- 

 ture is shown, the records are played on a special electric phono- 



