THE TALKING HEAD. 



137 



hack of the room. The three walls were painted in one colour, and a 

 subdued light increased the illusion, the effect of which was remarkable 

 (fig. 144). 



The spectres designed by Robin also attracted considerable public 



attention within recent times. They were images formed by the medium ot 

 transparent glass. Glass panes often produce the phenomenon of spectres. 

 In the evening, when it is dark out of doors, it is easy to prove that the 

 reflection of objects in a lighted room can be reproduced behind the window 

 panes by reason of the darkness outside. If we approach the window pane, 



