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APPENDIX. 



The result of this experiment was so successful that Mr. Stanford 

 determined to try another one on a more extended scale. He 

 assumed, if one picture could be taken instantaneously, why not an 

 indefinite number, and by increasing the number of cameras increase 

 to the same extent the number of views, and illustrate the various 

 positions in an entire stride ? 



Mr. Muybridge was authorized to procure the needed apparatus, 

 and a building suitable to the purpose was erected on the west side of 

 Mr. Stanford's private track at Palo Alto (see frontispiece). In the 

 following year, 1878, the preparations were complete; every resource 

 of the photographic art had been provided that was thought to be 

 required or attainable. Twelve cameras were placed in the building 

 at intervals of twenty-one inches, with double shutters to each. These 

 shutters were arranged, one above and the other below the opening 

 through which light was admitted to the lens, and held by india-rubber 

 springs, constructed in the form of a ring, with a lifting power of one 

 hundred pounds, and secured by latches, to be liberated on the com- 

 pletion of a magnetic current.* 



For the purpose of making the exposures at the proper intervals 

 of time, a machine was constructed on the principle of a Swiss music- 

 box, having a cylinder with a row of twelve pins arranged spirally. 

 This was put in motion by a spring, and, as it revolved, each pin in 

 succession established a magnetic circuit, with the magnet connected 

 with each of the twelve cameras in succession, and the whole series of 

 exposures was made in the time occupied by a single complete stride 

 of the horse. 



* This description of the shutters and their mode of action is somewhat obscure. The 

 shutter, as described by Kleffel (Handbuch der Practischen Photographic, Leipzig, 1874, p. 201), 

 is as nearly as possible the double shutter used by Muybridge. Kleffel's shutter was held by 

 a spring, and when the picture was to be taken the spring was touched, and the shutter, which 

 had an opening through its centre, dropped past the lens, exposing the lens to the light during 

 the time of the passage of the opening across it. He recommended weights to be used when 

 greater rapidity was required. Muybridge's modification of this consisted in the use of rubber 

 springs in lieu of weights as recommended by Kleffel ; though no claim is set up by him to 

 priority in the use of rubber springs, as one Thomas Skaife obtained a patent in England for 

 rubber springs for camera shutters as early as 1856. 



