SCIENCE IN THE INDUSTRIAL WORLD 



and nicety must be used. At a high speed the film 

 is fed rapidly behind the camera lens, the shutter of 

 which is operated by a small motor. The speed of 

 the shutter is such that from 900 to i, 800 separate pic- 

 tures must be taken every minute, or from fifteen to 

 thirty a second. Thus when any scene a procession 

 or a dramatic performance progresses in front of 

 the camera, a record will be obtained of the relative 

 position of objects in the camera field, say every one- 

 fifteenth of a second. 



The films used are either if or 2| inches in width, 

 and their length about fifty-five feet. Of course in 

 many instances a number of films have to be used to 

 reproduce a scene. Thus in the animated represen- 

 tation of a recent pugilistic encounter, which the whole 

 world was believed to be passionately longing to view, 

 the camera was operated steadily for one hour and 

 forty minutes, and in this time between six and seven 

 miles of celluloid film passed behind the winking lens. 



To reproduce the pictures, a positive strip is printed 

 directly from the developed negative, and this is passed 

 through the kinematograph, biograph, or other mov- 

 ing-picture machine in the same manner as the original 

 film is fed into the camera a rapid shutter exposing 

 the consecutive positions of the scene at the same 

 intervals as were used in photographing the original. 



The question will naturally be asked: What makes 

 the picture "move"? And in answering this it must 

 be first explained that the human eye is an absolutely 

 essential part of any chrono-photographic apparatus. 

 Let us take, for instance, the case of the kinemato- 



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