THE STEREOSCOPE : ITS HISTORY. 47 



and about sound-waves before the telephone came into existence. To 

 him distinctly belongs the credit of objectively demonstrating the 

 essential features of binocular vision, with the first instrument act- 

 ually constructed in accordance with principles which possibly others 

 might have applied, if they had possessed equal clearness of concep- 

 tion and fertility of invention. So slight was the general appreciation 

 of the fact that the two retinal images in binocular vision are dissimi- 

 lar, that Wheatstone made this discovery independently, and then 

 added the application which others had failed to make, but without 

 the knowledge that any one had preceded him in even forming the 

 conception. The originality of his discovery is not affected by the 

 unemphatic statements afterward found to have been recorded by 

 those who preceded him in thought but not in act. 



One of these predecessors was Mr. James Elliot, of Edinburgh, 

 who, "previous to or during the year 1834, had resolved to construct 

 an instrument for uniting two dissimilar pictures." By delay he lost 

 the golden opportunity, which, without envy or knowledge of his ex- 

 istence, was snatched away from him by Wheatstone. Not until 1839 

 did Elliot construct the instrument which he had contemplated. It 

 was simply a wooden box, open at the extremities, so that a pair of 

 conjugate pictures on glass could be placed at one end, and all light 

 except that which was transmitted through them could be excluded 

 from the eyes placed at the other end. He was not aware of Wheat- 

 stone's invention, which indeed did not become generally known for a 



Fig. 7. Brewster's Stereoscope, 1849. 



number of years after its completion, because not adapted for general 

 use, and because no other means than free-hand drawing existed for 

 the accurate preparation of the conjugate pictures. Those employed 

 by Wheatstone were outlines of various geometric solids. Elliot's 

 first stereograph was^a landscape, represented in Fig. 5, which is a 



