PHOTOGRAPHY, SCIENTIFIC ASPECTS 



glass disk on the periphery of which positives were 

 made. The disk was fitted with contact pins and was 

 rotated behind a slight opening, each picture, when it 

 came behind the opening, being illuminated by a spark 

 from a vacuum tube. 



Such, in brief, is the story of the development of 

 animated photography up to the time when a very 

 important invention revolutionized this, as well as 

 every other, branch of photographic art. As the reader 

 may have guessed, the flexible celluloid film, substi- 

 tute for the glass plate, is referred to. Marey now 

 employed a long roll of sensitive film fed behind, and 

 in the focus of, a photographic lens, and the same 

 contrivance was quickly adopted by Thomas A. Edi- 

 son in his kinetoscope. Edison is said to have con- 

 ceived the idea of the kinetoscope as early as 1887. 

 He at first proposed fixing the series of impressions on 

 the outer rim of a disk as in the case of the tachyscope, 

 but the tremendous advantage of the flexible film 

 caused him to abandon his first principle. The kinet- 

 oscope, patented in 1891, was quickly followed by 

 many other similar moving-picture machines with 

 which the public is familiar under various names 

 vitascope, vitagraph, biograph, phantoscope, kine- 

 matograph, etc. The last-named appeared in 1895, 

 and since that time no radical improvement has 

 been made in moving-picture machines, although 

 their use and popularity have enormously increased. 



The method of making moving pictures is compara- 

 tively simple in principle, although in matters of ad- 

 justment and other practical details the greatest care 



