new  Cafe  in  Squinting.  95 
twenty-fix  inches  from  it,  the  other  paper  became  invi- 
fible.  This  experiment  was  made  on  five  people  of 
various  ages,  from  ten  years  old  to  forty;  and  the  paper 
difappeared  to  them  all  at  about  this  diftance,  or  an  inch 
or  two  more  or  lefs:  but  to  mailer  sandford  the  paper 
difappeared  at  about  thirteen  inches  diftance  from  the 
wall.  Thefe  papers  were  afterwards  removed  to  twelve 
inches,  and  then  to  four  inches  interval  between  them ; 
and  by  the  niceft  obfervations  on  repeated  trials  I found, 
that  the  paper,  equally  with  one  eye  as  with  the  other, 
uniformly  difappeared  to  him  at  about  half  the  diftance 
it  did  to  five  others. 
Another  curious  circumftance  is,  that  as  large  a paper 
difappeared  to  him  at  half  the  diftance  as  it  did  to  others 
at  the  whole  diftance  ; and  hence  the  infenfible  part  of 
the  center  of  the  optic  nerve  in  his  eyes  is,  as  near  as  can 
be  eftimated,  four  times  the  area  of  the  infenfible  part 
of  the  eyes  of  other  people,  at  the  fame  time  that  the 
angle  made  between  the  ingrefs  of  the  optic  nerve  and 
the  bottom  of  the  eye  is  twice  as  great  as  in  others. 
It  is  eafy  to  conceive  that,  in  early  infancy,  when  any 
objedt  which  the  child  wifhed  to  infpedt  was  prefented 
obliquely  to  him,  that  on  this  firft  indiftindt  view  of  it, 
before  either  eye  could  be  turned  towards  it,  it  would 
appear  much  more  brilliant  and  diftindt  to  the  contrary 
eye,. 
