THE CINEMATOGRAPH 53 



a second, so that at least fifteen pictures are taken in every 

 second of time, and according to the requirements of illu- 

 mination and the rapidity of the movements of the men or 

 animals photographed this number may be greatly increased. 

 The film is developed, printed and fixed on a similar 

 rolling mechanism and the pictures are thrown one by one 

 by a powerful lantern on to a screen, and are jerked along 

 at the same rate as that at which they were taken, and are 

 magnified enormously. Animals and men in rapid move- 

 ment, railway trains, the waves of the sea are thus photo- 

 graphed, and when the serial pictures are thrown 

 successively on the screen the result is that the eye 

 detects no interval between the successive pictures the 

 figures appear as continuous moving objects. This is 

 due to the fact that whilst the impression produced on the 

 retina of the eye by each picture lasts for a tenth of a 

 second (less with brighter light), the interval between the 

 successive pictures is only one thirtieth of a second, and 

 accordingly the retinal impression has not gone or ceased 

 before the next is there ; hence there is no break in the 

 series of retinal impressions, but continuity.* 



It is this duration of the impression on the retina which 

 prevents us from separating or "seeing distinctly" the 

 successive phases of a horse's legs as he gallops by, and 

 has led to the remarkable result that no artist has ever 

 until twenty-five years ago represented correctly any one 

 phase of the movement of the legs in a galloping horse, 

 and it is doubtful whether that correctness is what the 

 painter of a picture really ought to put on his canvas. 

 If we examine the separate pictures of a galloping horse 

 as taken on a cinematograph film, we have before us 

 the actual record of the positions assumed by the legs 

 at intervals of the thirtieth of a second (or whatever less 

 interval and length of exposure may have been chosen), 



* See note on page 75. 



