INSTANTANEOUS PHOTOGRAPHY. 



23 



valuable time was consumed in arranging the threads for each 

 set of exposures; the time-intervals between successive exposures 

 were unequal and unrecorded ; plates were frequently wasted by 

 the subject making the exposures prematurely, or when the char- 

 acter of his motion was unsatisfactory : and, lastly, such a method 

 was impracticable for photographing wild animals and birds. 



To overcome these difficulties, Mr. Muybridge used a circuit- 

 breaker which he had devised and unsuccessfully tried in Cali- 

 fornia for making the successive electrical contacts automatically 

 and at equal intervals, long or short, as desired. This was used 

 throughout all the later work. A photograph of this machine, 

 which we shall call the contact-motor, is reproduced in Fig. 10. 



Fig. 10. 



Two vertical standards support a train of four multiplying 

 gears, to which motion is imparted by a weight hanging from a 

 cord wound on a drum fastened to the lowest shaft, P. Outside 

 of one of the standards, and concentric with the third shaft, is a 

 stationary ring or commutator, composed of twenty-four seg- 



