KNOWLEDGE. 



September, 1913. 



C D 



Figure 348. 

 The Principle of Ives's Parallax Stereograph. 



Figure 349. 



A Diagram illustrating Analogy 



between Ives's system and 



Elliott's Instrument. 



EA 



Figure 350. 



The Principle of Brewster's 

 Refracting Stereoscope. 



Figure 351. 



The Principle of Wheatstone's 

 Reflecting Stereoscope. 



CD 



Figure 354. 



The Principle of Pigeon's Prism 



Stereoscope. 



Figure 352. 

 The " Reflectascope." 



Figure 355. 



The constructive details of Pigeon's 

 Prism Stereoscope. 



4> 



Figure 353. 



Theodore Brown's pocket 

 Reflecting Stereoscope. 



Figure 356. 



The method of inspecting Pigeon 



Stereographs with an ordinary 



Plane Mirror. 



