CHAPTER VI. 



THE TELESTEREOGRAPH OF M. BELIN THE 

 EARLY WORK OF BELIN CHANGES IN HIS 

 SYSTEM RECENT EXPERIMENTS. 



ONE of the most indefatigable workers in the 

 field of photo -telegraphy is M. Edouard Belin, who 

 has been for some years actively engaged in work- 

 ing out a system of his own. His apparatus has 

 been designated the telestereograph, but as his 

 method of transmission has quite recently under- 

 gone a radical change, it will be better to describe 

 his first successful models by themselves. 



The use of a relief photograph, in which different 

 tones in the image are represented by different 

 thicknesses of the film, to vary the amount of 

 resistance in an electric circuit containing a suit- 

 able receiver, has been referred to in the intrto- 

 ductory chapter, and the idea is a very old one. 

 But the methods employed by Belin, both in the 

 mechanism for varying the resistance and in the 

 means of reception, were very ingenious, and he 

 obtained some promising results over artificial lines 

 and loop telephone lines, which unfortunately never 

 seemed to surpass a definite standard attained in 

 1908. 



