274 Mr. A. Claudet on Moving Photographic Figures. 



abruptness of two extreme movements, and from the deficiency 

 of intermediate positions. 



But nothing is so easy as to employ eight different pictures 

 in as many different stages of the action, and with this number 

 of pictures the effect will be sufficiently complete. For this, 

 having placed in the stereoscope two separate cubic frames, 

 revolving independently on the same horizontal axis, I have only 

 to fix on their four sides at right angles two sets of four pic- 

 tures, making eight pictures, which are made to pass in conse- 

 cutive order one after the other before the lenses of the instru- 

 ment, and the figure will appear to assume consecutively eight 

 different stages of the whole action. The cubic frames are 

 made to revolve by the motion applied to the slide which, as 

 is to be explained, transfers the sight alternately from one eye 

 to the other. The instrument in its simple state, with only two 

 pictures, will suffice to illustrate the principle, and at the same 

 time to elicit some curious phenomena of the perception of vision. 



It is known that the retina has the power of retaining for a 

 short time the impression or the sensation of the image which 

 has struck it. Now, availing myself of this property, I have 

 constructed the instrument in such a manner that, by means of 

 a slide with one hole, I can, by moving it rapidly in a recipro- 

 cating horizontal direction, shut one lens while the other remains 

 open ; and in continuing that motion, while one eye sees one of 

 the two pictures, the second eye cannot see the other picture. 



Now, if before the sensation of one eye is exhausted the slide 

 shuts the lens and opens the other, a new impression is pro- 

 duced on the retina, and we have an uninterrupted sensation of 

 vision, as if the object had moved before us ; and if a sufficient 

 number of pictures represent that object in the various consecu- 

 tive positions it has assumed during several stages of its motion, 

 we experience on the retina the same sensation we have when 

 we see the object itself while it is moving. For it must be ob- 

 served that although the pictures in their limited number do not, 

 and cannot, show all the intermediate positions of all the stages 

 of a continuing action, still the mind has the power of filling 

 up the deficiency, as it does if, when looking at a real object in 

 motion, we accidentally wink the eyes, or an obstacle happens 

 to pass between us and the object. Although during that short 

 interval we have lost the perception of a certain progress of the 

 action, the mind has, as it were, guessed and represented to itself 

 what ought to have taken place during the winking of the eyes, 

 or during the intervention of the passing obstacle, and by that 

 power of the mind there has been no interruption in the whole 

 perception. 



This is exemplified in the most forcible manner when we have 



