



ART VI. Account of an Optical Deception. 



[In a Letter to the Editor.] 

 SlB, 



THE optical phenomenon which I have here attempted to 

 represent, may amuse those of your readers to whom it is new, 

 and will probably serve to exercise the ingenuity of some in 

 attempting its solution. 



When a spoked wheel, such as that of a carriage, or the fly 

 of an engine, is viewed in motion, through a series of vertical 



