C. A. Young on Recurrent Vision. 268 
seen noticed. ‘The machine gives easily intense Leyden jar 
Li from seven to nine inches in length, and of most daz- 
P 
perfectly visible; and what is remarkable, every conspicuous 
object is seen éwice at least, with an interval of a trifle less than 
one-quarter of a second—the first time vividly, the second time 
faintly ; often it is seen a third, and sometimes, but only with 
great difficulty, even a fourth time. The appearance is pre- 
cisely as if the object had been suddenly illuminated by a light 
at first bright, but rapidly fading to extinction, and as if, while 
the ene lasted, the observer were winking as fast as 
sible 
I see it best by setting up in front of the machine, at a dis- 
tance of eight or ten feet, a white screen having upon it a black 
cross, with arms about three feet long and one foot wide, made 
of strips of cambric. That the phenomenon is really subjective, 
and not due to a succession of sparks, is easily shown by swing- 
ing the screen from side to side. The black cross, at all the 
measured roughly as follows: A tuning fork, making 9 
vibrations per second, was adjusted, so as to record its motion 
a 
Whatever the true explanation may turn out to be, the 
phenomenon at least suggests the idea of a reflection of the nerv- 
us impulse at the nerve extremities,—as if the intense impres- 
‘1on upon the retina, after being the first time propaga Si 
brain, were there reflected, returned to the retina, and from the 
: traveling again to the brain renewed the sensation. : 
have ventured to call the phenomenon “ Recurrent vision. 
