38 AN ESSAY ON 



PROPOSITION II. 



Objects, situated in the Common Axis, do not appear to 

 be in that Line, but in the Axis of the Eye, by which 

 they are not seen. 



THE facts which demonstrate the truth of 

 this proposition, are both numerous and com- 

 mon. If a piece of wire, or any other sub- 

 stance, representing a physical line, be placed 

 in the common axis, with one of its extremities 

 near to the visual base, and if both the optic 

 axes be directed to its farther or distant ex- 

 tremity, instead of one, two wires will be seen, 

 meeting each other at their farther ends, and 

 gradually diverging as they approach the face, 

 till they apparently terminate at the eyes. If 

 the right eye be closed, the wire which seemed 



coalesce either wholly or in part, as two sounds frequently do, 

 when heard at the same time by one ear 5 that consequently, 

 if the sounds of one musical instrument were to be heard by 

 one ear only, and those of another, by the other ear only, we 

 could have little or no perception of harmony from such 

 sounds -j and that, if in any succession of sounds emitted by 

 one instrument, we were to hear the 1st, 3d, 5th, and so on, 

 by one ear only, and the 2d, 4th, 6th, and so on, by the other 

 ear only, we should be deprived, in a considerable degree, of 

 the melody of such sounds, as this seems to depend in a great 

 measure upon a new impression being made upon the audi- 

 tory nerve by one sound, before the impression of the sound 

 immediately preceding has passed away. 



