272 Mr. A. Claudet on Moving Photographic Figures. 



Binocular pictures of persons dancing, fencing, or boxing, of 

 acrobats at their wonderful feats, of boys playing at different 

 games, all in the various stages of the action of each sport, repre- 

 senting consecutively the whole performance — such pictures 

 might have been supposed to be invaluable as calculated to ex- 

 hibit the stereoscopic illusion of persons in the real action of life. 

 Therefore the solution of such an interesting problem was capable 

 of exciting the emulation and the ambition of many ingenious and 

 scientific minds. 



Among those who undertook the task, M. Duboscq, the emi- 

 nent optician of Paris, was the one who attained the greatest 

 success. He had fixed the two series of binocular photographs 

 on two zones of the revolving disk of the phenakistoscope, one 

 above the other ; and by means of two small mirrors placed each 

 respectively at the inclination capable of reflecting the two zones 

 on the same horizontal line, from thence the images could each 

 separately meet the axis of each of the two prismatic lenses of 

 the stereoscope. In this manner, during the revolution of the 

 disk each eye had separately the perception of one of the series 

 of photographs, each showing the perspective of one eye, and the 

 stereoscopic effect of figures in motion was consequent. 



M. Duboscq gave another form to the phenakistoscope. 

 Instead of the vertical original revolving disk of Plateau, he 

 employed a cylinder revolving on its vertical axis ; and he placed 

 on two inside zones of that cylinder, one above the other, the 

 two series of photographic pictures, between the slits through 

 which the eyes can see the pictures ; and by means of two mir- 

 rors, as in the other apparatus, each series was reflected on its 

 respective lens through the cylinder, and the stereoscopic effect 

 was produced in combination with the phenakistoscopic effect. 



However, these two attempts of M. Duboscq present a few 

 imperfections, which we are going to explain. In the revolving 

 disk the two series of pictures do not move with the same velo- 

 city, on account of their being placed on two zones of different 

 peripheries ; and this produces a sort of confusion and distortion 

 in the representation of the object during its movement. The 

 same defect exists in Plateau's phenakistoscope in the perception 

 of its single series ; for the top and bottom parts of the figures, 

 owing to the cause explained, revolving with different velocities, 

 are not impressed on the retinae during the same time ; and the 

 blank spaces between the pictures, being larger for the top than 

 for the bottom part, give a stronger sensation of void during the 

 visual perception of the pictures. 



In the revolving cylinder this defect does not occur; but the 

 pictures being considerably curved, like the cylinder, is a most 

 unfavourable disposition for examining them in the stereoscope ; 



