170 Professor William Stirling [^I^y 12, 



produce a complete fusion. There are two kinds of "flicker" before 

 complete fusion is obtained : " coarse " flicker, which has a certain 

 glittering character, and a " fine " flicker, passing into complete 

 fusion of sensations. 



Zoetrope, Cinematograph, and their Predecessors. 



On this principle is constructed the well known " wheel of life," 

 or " zoetrope." If the successive phases of a movement be drawn on 

 a glass disk, and this disk be rotated in relation to an opaque disk 

 with a slit in it, then on looking through the slit one sees the object 

 as if it were in motion. This is the stroboscopic method, of which I 

 will show you some striking yet simple examples. 



The thaumatrope of Dr. Paris (1827) — now adapted as a children's 

 toy— was an early precursor of the zoetrope, and consisted of a rect- 

 angular plate or card which is held Ijetween two strings and made to 

 twirl. A cage is sketched on one side and a bird on the other. On 

 rotating the plate on its vertical axis, the bird appears to be in 

 the cage. 



The stroboscope of Stampfer, and the corresponding apparatus of 

 Plateau, which he called a " phanakistoscope," are well known. It 

 appears that Plateau was led to invent his stroboscopic disk by some 

 observations of Faraday on revolving wheels and disks and their 

 appearances, published in 1831 in the first volume of the "Journal 

 of the Royal Institution." Plateau sent an example of his apparatus 

 through M. Quetelet to Faraday in 18o2. 



Naturally, with the development and perfecting of instantaneous 

 photography first upon glass, and then on flexible sensitized films, 

 this method lent itself admirably to the preparation of instantaneous 

 photographs. If a series of pictures be taken one after the other, 

 representing the successive phases of a motor event, it is obvious that 

 if these pictures be re-presented to the eye with sufficient rapidity 

 they will Ije fused, and the observer will see on the screen a repre- 

 sentation of the original movement. 



Helmholtz, in the second edition of his " Haudbuch der physio- 

 logischeu Optik" (181)G), speaking of instantaneous photography, 

 mentions the work of Muybridge and Anschlitz, gives a picture of a 

 horse jumping a hurdle, and adds " Diese Bilder sind auch fiir das 

 Studium der thierischen BeAvegungen wichtig." We have travelled a 

 long way since then. 



It is not with cinematography as a method for the representation 

 of pageantry, or faked pictures, or spectacular drama in dumb show, 

 or for the detection of crime, that I wish to deal to-night, but rather 

 with this art as useful for showing reproductions of physiological and 

 biological experiments to large audiences either in school, college, 

 institution, or university, and also as a means of solving some of the 

 features in movements that, because of their rapidity, cannot be 

 analysed by other means. 



