318 MOVEMENT 



an analyzing apparatus. Instead of the small fenestra- 

 tions on the circular diaphragms, long slits should be 

 made, occupying a third of their circumference. 

 During this long exposure, the film should be com- 

 pletely arrested, and for this purpose the compressor 

 should have a particular kind of cam. 



To realize the nature of a movement satisfactorily, 

 it is as well to reproduce it several times. This may 

 easily be done by an apparatus fitted with revolving 

 discs ; but, as in our apparatus, we have to use a length 

 of film, it should be glued together at the ends, 

 so as to produce an endless series of images continually 

 rotating at the focus of the objective. Such a strip as 

 this could not be introduced into the ordinary chrono- 

 photographic apparatus. 



We have therefore constructed a special apparatus, 

 in which an endless length of film containing forty or 

 sixty figures, or even more, is allowed to pass with- 

 out cessation under the field of the objective. 



The illumination, which is from behind, and consists 

 either of the electric light or the sun itself, projects 

 these figures upon a screen. This instrument produces 

 very bright images, but it is noisy, and the projected 

 figures do not appear as absolutely motionless as one 

 could wish. 



Having arrived at this point in our researches, we 

 learned that our mechanic had discovered an im- 

 mediate solution of this problem, and by quite a 

 different method ; we shall therefore desist from 

 our present account pending further investigations. 



